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ISLANDS, 1900 TO 1906 




London: CHAPMAN & HALL, Limited 



i wo Gooies Kect)iv<M 

OCT 2 

IwOiurt.jtm lijiui 



Stanbope lpress 



In preparing the material for a lecture on Charts for 
Columbia University, the writer was impressed with the 
fact that although nautical charts are mentioned or dis- 
cussed in many publications, there was not found any one 
which covered the general subject of their origin, con- 
struction, and use. In the countries of the world more 
than a million copies of such charts are now issued 
annually. A considerable portion of the human race is 
interested directly or indirectly, whether as mariners 
or passengers or shippers, in navigation upon the sea. 
Aside from supplying a handbook for those who might 
have a general interest in the subject, it was thought 
that a discussion of charts might lead to further con- 
sideration of the principles governing their construction. 

This paper has intentionally been made as non- 
technical as seemed feasible in treating a somewhat 
technical subject. The writer is indebted to the Coast 
and Geodetic Survey for various illustrative material 
from its archives, and to a number of authors for facts 
or suggestions. A list is appended of books and papers 
which have been freely consulted, bearing on this and 
related subjects. 

G. R. P. 

Washington, D.C., May 24, 1908. 

Digitized by the Internet Archive 
in 2011 with funding from 
The Library of Congress 



List of Books or Papers bearing on Nautical Charts 


Charts and Maps 1 

Collection of Information for Charts 31 

Preparation of Information for Charts 67 

Publication of Charts 84 

Correction of Charts 97 

Reading and Using Charts 112 

Use of Charts in Navigation 124 

Publications Supplementing Nautical Charts 154 

Index 161 


Periplus, an Essay on the Early History of Charts, and Sailing 

Directions. A. E. Nordenskiold, Stockholm, 1897. 
Maps, their Uses and Construction. G. James Morrison, London, 

Charts and Chart Making. Lieut. John E. Pillsbury, U.S.N., in 

Proceedings U . S. Naval Institute, 1884. 
Principal Facts relating to the Earth's Magnetism. L. A. Bauer, 

in U. S. Magnetic Declination Tables, Coast and Geodetic 

Survey, 1903. 
Marine Hydrographic Surveys of the Coasts of the World. G. W. 

Littlehales, in Report of the Eighth International Geographic 

Congress, 1904. 
Smithsonian Geographical Tables. R. S. Woodward, Washington, 

Admiralty Charts, Abridged list of. Published by J. D. Potter, 

London, 1907. 
Military Topography. Capt. C. B. Hagadorn, U.S.A., West Point, 

Service Hydrographique de la Marine, Paris, 1900. 
A Manual of Conventional Symbols in Use on Official Charts. 

United, States Hydrographic Office, Gustave Herrle, 1903. 
Hydrographical Surveying. Admiral W. J. L. Wharton, London, 

On the Correction of Charts, Light Lists, and Sailing Directions. 

Published by J. D. Potter, London, 1904. 
Notes Relative to the Use of Charts. D. B. Wainwright, Coast 

and Geodetic Survey, 1900. 

viii Books or Papers on Nautical Charts 

The Law relating to Charts and Sailing Directions. H. Stuart 
Moore, London, 1904. 

Notes bearing on the Navigation of H. M. Ships. Hydrographic 
Office, London, 1900. 

The Relations of Harbors to Modern Shipping. W. H. Wheeler, 
in Engineering News, September 6, 1906, New York. 

Wrinkles in Practical Navigation. Capt. S. T. S. Lecky, London, 

Navigation and Compass Deviations. Commander W. C. P. Muir, 
U.S.N., Annapolis, 1906. 

The Practice of Navigation. Henry Raper, London, 1898. 

Lehrbuch der Navigation. Reichs-Marine-Amt, Berlin, 1906. 

The Nautical Magazine, London. 

Dangers and Ice in the North Atlantic Ocean. Bureau of Naviga- 
tion, U. S. Navy Department, 1868. 

Reported Dangers in the North Pacific Ocean. U. S. Hydro - 
graphic Office, 1871. 

Pacific Islands, Vol. Ill, chapter on "Vigias." British Hydro- 
graphic Office, London, 1900. 

Harriman Alaska Expedition, Vol. II, Bogoslof, our Newest Vol- 
cano, by C. Hart Merriam, New York, 1901. 

Expedition to the Aleutian Islands, 1907. T. A. Jaggar, Jr., in 
The Technology Review, 1907, Boston. 

Recent Changes in Level in the Yakutat Bay Region, Alaska, by 
R. S. Tarr and Lawrence Martin, in Bulletin of the American 
Geological Society, 1906. 

An Index to the Islands of the Pacific Ocean. W. T. Brigham, 
Honolulu, 1900. 

Geography, articles by C. R. Markham, A. R. Clarke, and H. R. 
Mill in Encyclopaedia Britannica. 

Development in Dimensions of vessels, Elmer L. Corthell, 
Tenth International Navigation Congress, 1905. 



Need of maps. Maps are useful and necessary for 
many purposes. Only by means of a correct map 
or globe can a clear idea of the geography of a region 
be given. An attempt to convey the same information 
by a written description would in comparison be both 
cumbersome and obscure. Even by passing over an 
extensive region a man unaided by instruments will 
obtain only a rather crude notion of the relations, which 
he could clearly see on a good map. The importance 
among the human arts of the making of maps is indi- 
cated by the references to them in very early historical 
records, and by the skill in map drawing shown by 
some of the primitive peoples of to-day. This skill 
exists particularly among races whose mode of life 
gives them a wide horizon, as for instance the Eskimos. 
An interesting instance of this was the case of Joe, an 
Eskimo guide, who, in 1898, before the surveys of the 
Yukon delta were made, drew a map of the Yukon 
mouths with much more complete information than any 
previously available. 

Without attempting to enumerate in detail the special 
uses for maps, in the broader sense they may be said 
to be essential for commercial, engineering, military, 
scientific, educational, and political purposes. 

2 Charts and Maps 

Early geography and map making. The oldest map 
known is a plan of gold mines in Nubia, drawn on a 
papyrus. This is of the thirteenth century B.C., and 
was found in Egypt. 

In the earliest historic times men believed the earth 
to be a flat surface of nearly circular outline, a natural 
inference for those with limited outlook and communi- 
cation. Later the idea was introduced of the ocean as 
a river bounding the earth disk. The spherical theory 
of the earth was, however, early accepted by learned 
men, and was demonstrated by Aristotle (384 to 
322 B.C.), who used as proofs the earth's shadow on the 
moon, and the change in the visibility of the stars in 
traveling north or south. Crates constructed a terres- 
trial globe in the second century B.C. 

There is no Greek or Latin map extant of earlier 
date than the time of Ptolemy, but there are references 
showing that maps were in use. One of the first of 
such passages in Greek literature is the interesting 
comment of Herodotus written in the fifth century B.C., 
"but I laugh when I see many who already have drawn 
the circuits of the earth, without any right understanding 
thereof. Thus they draw Oceanus flowing round the 
earth, which is circular, as though turned by a lathe, 
and they make iVsia equal to Europe." 

A map of the world was drawn by Anaximander, 
560 B.C. A hundred years later Demoeritus drew a 
map having an oblong shape, and taught that the width 
of the world from east to west was one and a half times 
its extent from north to south, a conclusion based on 
his travels eastward as far as India. This theory, 
which was for a time accepted, has left an enduring 

Early Geography and Map Making 3 

mark in the words longitude and latitude, originally 
signifying the length and the breadth of the earth. 

The first application of astronomy to geography was 
made by Pytheas, who about 326 B.C. obtained the lati- 
tude of Marseilles by an observation of the altitude of the 
sun. Dicearchus in 310 B.C. determined the first parallel 
of latitude by noting places where on the same day the 
sun cast shadows of equal length from pillars of equal 
height. Eratosthenes (276 to 196 B.C.) was the first 
to compute the circumference of the earth from obser- 
vations of the altitude of the sun at Alexandria and at 
Syene in Upper Egypt and an estimation of the distance 
between these two places. Ptolemy, a Greek of Alexan- 
dria, in the years from 127 to 151 a.d. wrote extensively 
on geographic subjects, and collected into systematic 
form all geographic knowledge then existing; he was 
the greatest geographer of early history. 

In the ten centuries which followed, part of the early 
advance in this science was obscured, and the theory 
that the earth was a flat disk surrounded by the sea 
again became prevalent. The voyages of discovery 
of the middle ages, however, led to a rapid develop- 
ment of geographic knowledge. 

The flattening of the spherical earth was not sus- 
pected until in 1672 a clock regulated to beat seconds 
at Paris, when taken to Cayenne near the equator was 
found to lose two and one-half minutes a day. New- 
ton proved that this was due to the fact that the earth 
is an oblate spheroid. In 1735 accurate measurements 
were undertaken to determine the size and shape of 
the earth. The equatorial diameter has been found 
to be 7926.6 miles and the polar diameter 7899.6 miles, 

Charts and Maps 

the difference, or 27 statute miles, being the amount of 
the flattening at the poles. 

The first sailing directions. The early Greek and 
Roman writers do not allude to charts or maps intended 
especially for the use of seafarers. There are, however, 
extant several peripli or descriptions of the coast. Some 
of these appear certainly to have been intended for use 
as nautical guides, corresponding to the modern sail- 
ing directions. It is probable that they were explan- 
atory of or accompanied by coast charts, now lost. 
They are of interest therefore as being probably the first 
compilations for the guidance of seamen. One of the 
earliest, written apparently in the fifth and fourth 
centuries B.C., is entitled "Scylax of Caryanda, his 
circumnavigation of the sea of the inhabited part of 
Europe and Asia and Libya." It contains a systematic 
description of the coasts of the Mediterranean, Black 
Sea, and part of the west coast of Africa. The fol- 
lowing are some extracts which indicate the character 
of the work. It is to be noted that no bearings are 
given, and that distances are usually stated by day's 
sail; Africa is referred to as Libya. 

" Europe. I shall begin from the Pillars of Hercules 
in Europe and continue to the Pillars of Hercules in 
Libya, and as far as the land of the great Ethiopians. 
The Pillars of Hercules are opposite each other, and are 
distant from each other by one day's sail. . . . From 
Thonis the voyage to Pharos, a desert island (good 
harborage but no drinking water), is 150 stadia. In 
Pharos are many harbors. But ships water at the 
Marian mere, for it is drinkable. . . . From Cher- 
sonesus is one day's sail; but from Naustathmus to 

The First Sailing Directions 

the harbor of Cyrene, 100 stadia. But from the harbor 
to Cyrene, 80 stadia; for Cyrene is inland. These 
harbors are always fit for putting into. And there are 
other refuges at little islands, and anchorages and many 
beaches, in the district between. . . . After the isthmus 
is Carthage, a city of the Phoenicians, and a harbor. 
Sailing along from Hermsea it is half a day to Carthage. 
There are islands off the Hermsean cape, Pontia island 
and Cosyrus. From Hermsea to Cosyrus is a day's 
sail. Beyond the Hermsean cape, towards the rising 
sun, are three islands belonging to this shore, inhabited 
by Carthaginians; the city and harbor of Melite, the 
city of Gaulus, and Lampas; this has two or three 
towers. . . . The sailing along Libya from the Canopic 
mouth in Egypt to the Pillars of Hercules . . . takes 
74 days if one coast round the bays. . . . From the 
cape of Hermsea extend great reefs, that is, from Libya 
towards Europe, not rising above the sea; it washes 
over them at times. . . . From Thymiateria one sails 
to cape Soloes, which juts far into the sea. But all 
this district of Libya is very famous and very sacred. . . . 
This whole coasting from the Pillars of Hercules to 
Cerne Island takes twelve days. The parts beyond the 
isle of Cerne are no longer navigable because of shoals, 
mud, and sea-weed. This sea-weed has the width of 
a palm, and is sharp towards the points, so as to prick." 
That there were many other similar writings in the 
following centuries is shown by the following quotation 
from Marcianus, in a preface to sailing directions 
written in the fifth century a.d.: "This I write after 
having gone through many sailing directions, and spent 
much time on their examination. For it behooves all 

Charts and Maps 

who are men of education, to scrutinise such attempts 
at learning in this subject, so as neither rashly to believe 
the things that are said, nor incredulously to set their 
private opinions against the careful decisions of others." 

The oldest extant sailing directions of the middle 
ages bear date 1306 to 1320. 

Development of chart making. The application of 
the compass to nautical use in the twelfth century 
a.d. had a marked effect in encouraging voyages of 
exploration, and therefore indirectly on chart making. 
The following, written toward the close of the twelfth 
century, is the first known mention of the use of the 
compass in Europe: "The sailors, moreover, as they sail 
over the sea, when in cloudy weather they cannot longer 
profit by the light of the sun, or when the world is 
wrapped in the darkness of the shades of night, and 
they are ignorant to what part of the horizon the prow 
is directed, place the needle over the magnet, which 
is whirled round in a circle, until, when the motion 
ceases, the point of it (the needle) looks to the north." 
The nautical compass of that time appears to have 
consisted of a magnetized needle, floated in a vessel 
of water by a cork or reed, and having no index 
nor compass card. Peregrinus in 1269 made notable 
improvements in the compass, including a pivot sus- 
pension for the needle, a graduation, a lubber line, 
and an azimuth bar for sighting on the sun or other 

Nautical charts are known to have been in use since 
the thirteenth century a.d., but the earliest extant of 
which the date can be fixed is Vesconte's loxodromic 
chart of 1311. 

Development of Chart Making 

The loxodromic charts first appeared in Italy, and 
were so called from the fact that they were crossed by 
loxodromes (or rhumb lines) radiating from a number 
of crossing points distributed regularly over the map. 
Compass roses carefully drawn were later added at these 
crossing points, the first appearing on a chart of 1375. 
The earliest known mention of the variation of the 
compass from true north was on the first voyage of 
Columbus, who discovered this important fact in 1492, 
and as a consequence his "seamen were terrified and 
dismayed." Before that time it was assumed in Europe 
that the compass pointed "true to the north pole." 
The apparent failure to detect the variation earlier was 
doubtless to some extent due to its small amount at 
that time along the Mediterranean. The earlier charts 
showed both lines and compass roses apparently 
oriented with the true meridian, though there is some 
evidence to indicate that they were actually oriented 
with the magnetic meridian, the designer not recognizing 
any difference. The variation of the compass was first 
marked on a map in 1532 and on a printed chart in 
1595, but the placing of magnetic compasses on charts 
did not become customary until about fifty years ago. 
These early charts were drawn on parchment, using 
bright colors. They were copied by hand, one from 
another, with gradual variations. They had no pro- 
jections, and the draftsmen evidently had no idea of 
the sphericity of the earth. Islands and points were 
usually exaggerated; shallows were indicated, but no 
soundings; no information was given as to the interior 
of the countries ; a scale of distances was nearly always 

Charts and Maps 

Charts were first printed about 1477, and are known 
to have been engraved on copper by 1560. 

The maps of Ptolemy were ruled with degree lines, 
but no chart was so provided until 1427; by 1500, 
however, most charts were graduated. Before this 
date it is not known on what projection the charts 
were constructed. On the first graduated charts the 
degree lines were equidistant parallel straight lines 
cutting each other at right angles and thus dividing 
the chart into equal squares or rectangles. These 
were known as " plain charts." This square projection 
had little to commend it save simplicity of construction, 
as in higher latitudes it gave neither directions nor 
distances correctly. The difficulties of its use in nav- 
igation were early recognized, and nautical works con- 
tained chapters on "sailing by the plain chart, and the 
uncertainties thereof." 

The example of early chart making shown in Fig. 2 
is of great interest as being the earliest extant chart 
which includes America. This chart was drawn on 
ox-hide in 1500 by Juan de la Cosa, who accompanied 
Columbus on his first voyage as master of his flagship, 
and on his second voyage as cartographer. The chart, 
of which only a portion is shown here, purports to 
cover the entire world ; it joins Asia and America as one 
continent, the Pacific Ocean being then still unknown. 

Gerhard Kramer, a Flemish map-maker, better 
known by his Latin name of Mercator, in 1569 pub- 
lished his famous Universal Map. In this map the 
meridians and parallels were still straight lines inter- 
secting at right angles, but the distances between the 
parallels were increased with increasing latitude in 



Development of Chart Making 9 

such proportion that a rhumb line, or line cutting the 
meridians at a constant angle, would appear on the 
map as a straight line. Mercator never explained 
the construction of his chart, and as the above condition 
was not accurately carried out, it is thought that the 
chart was drawn by comparing a terrestrial globe 
with a "plain chart." After examination of a merca- 
tor chart in 1590, Edward Wright developed the cor- 
rect principles on which such a chart should be 
constructed, and published in 1599 his treatise "The 
Correction of Certain Errors in Navigation." It took 
nearly a century to bring this chart into use, and even 
in the middle of the eighteenth century nautical writers 
complain that " some prefer the plain chart." 

The Arcano del Mare, 1646, was the first marine 
atlas in which all the maps were drawn on the merca- 
tor projection. 

In the sixteenth, seventeenth and eighteenth centuries 
charts and sailing directions were often bound together 
in large volumes. These usually had quaint titles, not 
overburdened with modesty, of which the following is 
an example: " The Lightning Columne, or Sea-Mirrour, 
containing the Sea-Coasts of the Northern, Eastern, 
and Western Navigation. Setting forth in divers 
necessaire Sea-Cards, all the Ports, Rivers, Bayes, 
Roads, Depths, and Sands. Very curiously placed on 
its due Polus height furnished. With the Discover- 
ies of the chief Countries and on what Cours and Dis- 
tance they lay one from another. Never there to fore 
so Clearly laid open, and here and there very diligently 
bettered and augmented for the use of all Seamen. 
As alsoo the situation of the Northerly Countries, as 

10 Charts and Maps 

Islands, the Strate Davids, the Isle of Jan Mayen, 
Bears Island, Old Greenland, Spitsbergen and Nova 
Zembla. Adorneth with many Sea-Cards and Dis- 
coveries. Gathered out of the Experiences and prac- 
tice of divers Pilots and Lovers of the famous Art of 
Navigation. Where unto is added a brief Instruction 
of the Art of Navigation, together with New Tables 
of the Sun's Declination, with a new Almanach. At 
Amsterdam. Printed by Casparus Loots-Man, Book- 
seller in the Loots-Man, upon the Water. Anno 1697. 
With Previlege for fiftheen years." 

In 1633 a cartographer was appointed to the States- 
General of Holland, and it was his duty to correct the 
charts from the ships' logs. The Dutch at an early 
date made important progress in publishing charts. 
In 1720 there was established in Paris by order of the 
king, a central chart office ("depot des cartes et plans, 
journaux et memoires concernant la navigation "), and 
in 1737 the first charts were published by this office. 
Detailed surveys of the coast of France were com- 
menced in 1816. 

In 1740 " the commissioners for the discovery of 
longitude at sea" were authorized by Parliament to 
expend money on the survey of the coasts of Great 
Britain, this commission having been created in 1713. 
Various rewards were offered by this commission, 
including one of £10,000, for the discovery of a method 
of determining the longitude within 60 miles, an inter- 
esting side light on the uncertainties of navigation at 
that time. Compensated timepieces, which have been 
so important a factor in improving navigation, were 
invented by Harrison about 1761. 

Development of Chart Making 13 

In 1795, by an Order in Council, a Hydrographical 
Office was established in London, " to take charge and 
custody of such plans and charts as then were, or should 
thereafter be, deposited in the Admiralty, and to select 
and compile such information as might appear to be 
requisite for the purpose of improving navigation." 
This office had at first one assistant and one draftsman. 
Before that time many charts of a private or semi- 
official character had been published; the catalogue of 
the East India Company in 1786 included 347 charts. 

In 1807 the Congress of the United States authorized 
the President "to cause a survey to be taken of the 
coasts of the United States, in which shall be designated 
the islands and shoals, with the roads or places of 
anchorage^ within twenty leagues of any part of the 
shores of the United States; and also the respective 
courses and distances between the principal capes, or 
headlands, together with such other matters as he may 
deem proper for completing an accurate chart of every 
part of the coasts within the extent aforesaid." This 
law was the origin of the present United States Coast 
and Geodetic Survey, now under the Department of 
Commerce and Labor. 

In 1841 a systematic survey of the Great Lakes was 
commenced; this is the Survey of the Northern and 
Northwestern Lakes, briefly known as the Lake Survey, 
conducted under the Corps of Engineers. 

In 1866 the United States Hydrographic Office was 
established under the Navy Department "for the 
improvement of the means for navigating safely the 
vessels of the Navy, and of the mercantile marine, by 
providing under the authority of the Secretary of 

14 Charts and Maps 

the Navy, accurate and cheap nautical charts, sailing 
directions, navigators, and manuals of instructions for 
the use of all vessels of the United States, and for the 
benefit and use of navigation generally." 

Systematic surveying and chart making date back 
little more than a century, and most of the information 
shown on modern charts has been gathered in that 
time. At present all the principal maritime nations of 
the world have made, or are extending, careful surveys 
of their own coasts. 

Several of the countries have added valuable contri- 
butions in the examination of other regions and oceanic 
areas beyond their borders. The maritime and colonial 
interests of Great Britain impelled that nation to carry 
on extensive surveys along coasts whose inhabitants 
were not prepared to do this work in the earlier days; 
the British have made surveys along the coasts of Asia 
and Africa and a part of South America, and the result- 
ing charts have been a very important and not suffi- 
ciently known contribution to commercial intercourse 
among the nations, as well as to geography. 

The Dutch, French, Spanish, and other European 
governments have made nautical surveys in various 
parts of the world, largely in connection with their own 
colonies, and in recent years much useful work has 
been done by vessels of the German government. The 
United States has also beyond its own territory made 
valuable additions to hydrographic knowledge in the 
work of officers of the Navy in a number of oceanic 
exploring expeditions, and surveys on the coasts of 
Mexico and in the West Indies, and in the explorations 
of Fish Commission vessels. 

Progress of Hydrographic Surveys 17 

Extension of maritime surveys. Of the total area of 
the earth's surface, 51,886,000 square miles is land and 
145,054,000 square miles is sea. The oceans thus 
occupy nearly three-fourths of the whole surface, afford- 
ing highways open to the nations. To conduct inter- 
national commerce by water the ships of one country 
must enter the ports of another. Thus both on the 
open sea and in the harbors there is an interest, common 
to seamen of all nationalities, in the advance of marine 
surveys and in the publication of charts. 

To keep the coasts properly charted, as well as lighted 
and buoyed, is an obligation devolving on modern 
nations, not only for the benefit of their own commerce 
but for that of other countries. 

As shown below, only a small part of the coast line 
of the world is thoroughly surveyed. In the extensive 
ocean areas which are dotted with islands or reefs, a large 
amount of work is required for their sufficient charting, 
although many doubtful areas have been cleared up in 
recent years. Even the parts that are known to be of 
depths so great as to be free from navigational dangers 
should be sounded over sufficiently to develop the gen- 
eral configuration of the ocean bottom. 

Through international understanding a thorough 
exploration of all the water area of the globe and the 
coasts may in time be effected, and the many doubtful 
spots which still disfigure the charts may be either 
eliminated or definitely located. 

Present state of progress of hydrographic surveys. A 
comparatively small proportion of the coasts of the 
world can be considered as completely surveyed at the 
present time, and even such regions require much 

18 Charts and Maps 

additional revision. In the class of more thoroughly 
surveyed coasts should be included the Atlantic and 
most of the Pacific coast of the United States, Porto 
Rico, nearly all the coasts of Europe, Algeria, and 
portions of the coasts of Japan, the Philippine Islands, 
and India. 

A large part of the world's coasts has been surveyed 
incompletely, but sufficiently well to permit the publi- 
cation of navigational charts. This is the condition as 
respects most of southeastern Alaska and some other 
portions of the Alaskan coast, British Columbia, most 
of Mexico, Central America, the West Indies, Brazil 
and parts of Chile, the Hawaiian Islands, China, Malay 
Peninsula, Siam, the Dutch East Indies, Australia, 
New Zealand, Persia, Arabia, most of Africa, Iceland, 
northern Scandinavia, and Finland. 

Another considerable portion of the coasts has not 
been surveyed, but has been covered by explorations 
which have been embodied in nautical charts of varied 
degrees of incompleteness. In this class are the north 
coast and considerable portions of the south and west 
coasts of Alaska, the Aleutian Islands, Siberia, most of 
the oceanic groups in the Pacific, the northern coasts 
of Europe and North America, Greenland, the west 
coast of South America, Venezuela, and Argentina. 

Only a very small proportion of the total length of 
coasts is now entirely unexplored, and such portions 
are confined to the polar regions. 

Chart publications of various nations. There are 
about eighteen nations publishing navigational charts, 
and adding to the information on which charts are 
based. Many of these nations republish to some extent 

Systems in Use on Various Charts 19 

the charts prepared by the others. Great Britain has 
kept up a series of charts covering all parts of the world 
and practically including in some form all information 
published elsewhere. This series now (1908) includes 
3725 different charts, of which the annual issue is 
about 600,000 copies. France (1906) publishes 2948 
different charts. 

In the United States, charts are published by the 
Coast and Geodetic Survey for the coasts and tidal 
waters of the main country and the insular possessions, 
by the Hydrographic Office for oceanic areas and for- 
eign coasts, and by the Lake Survey for the Great Lakes. 
The total number of different charts issued by these 
bureaus is about 2300, and the total annual issue is 
about 225,000 copies. 

Systems in use on various charts. 

Longitude. The first chart of New York, published 
by the Coast Survey in 1844, was referred to the City 
Hall of New York as the initial longitude, and some 
years ago it was the prevailing custom for each nation 
to use a local initial longitude. While this satisfied 
local pride it led to much geographical and naviga- 
tional confusion. Happily the charts of all countries 
are now referred to Greenwich, with the following 
exceptions : 

France refers to Paris, which is 2° 20' 15" E. of Greenwich. 
Spain refers to San Fernando, which is 6° 12' 20" W.of Greenwich. 
Portugal refers to Lisbon, which is 9° 08' 24" W. of Greenwich. 

Units for depths. The English fathom or foot is used 
for depths on the charts of Great Britain, the United 
States, and Japan. Russia uses the sajene of seven 

20 Charts and Maps 

English feet. On the modern charts of practically all 
the other countries the meter is used, though on older 
charts various units are found. 

In the first group feet are ordinarily found only on 
large scale or local charts of areas with moderate 
depths, and the other charts are in fathoms, except 
that on the earlier charts of the Coast and Geodetic 
Survey feet were used on a sanded surface inside of the 
three-fathom curve and fathoms on the white surface 
outside of that curve. Heights are stated in feet on 
the charts of the first group. 

Plane of reference. As the depth of water varies 
with the tide, it is necessary for charting purposes to 
adopt some standard plane to which the soundings are 
referred. Practically all countries have adopted for 
this purpose a low stage of the tide, as this is obviously 
on the side of safety; in most cases an extreme low 
water is used, so that the actual depths will seldom, 
owing to the tide, be less than those shown on the chart. 
The definite reference planes used on the American 
charts will be mentioned later. 

On nearly all charts heights are referred to mean high 
water, doubtless owing to this being the visible limit of 
the land at high tide. On topographic maps of the 
interior, the heights are referred to mean sea level, 
which plane is of course lower than the preceding by 
one-half the range of tide. 

Symbols on charts. Fair uniformity as to general 
principles, with differences as to details in carrying 
them out, exists on the various series of charts regard- 
ing their general arrangement and the more important 
symbols, such as in the shading of land to distinguish 

Desirability of Ufiiformity in Charts 21 

from water, the use of depth curves, the representation 
of hills by shade or contour, the indication of shoals 
and dangers, and of lighthouses and buoys. 

Desirability of uniformity in charts. Ships engaged 
in international commerce must enter foreign ports. 
As the information is constantly changing and charts 
are being corrected or improved, it is sometimes 
desirable for the navigator to consult the local foreign 
charts, and it may often be necessary for him to carry 
in his chart room the charts of several different coun- 
tries. There are therefore important advantages in 
international uniformity in chart publication. 

There should be a common initial longitude, and as 
the longitude of Greenwich has been so extensively 
adopted, it appears quite probable that its use may 
some day become universal. 

A common unit for soundings and heights would be 
very desirable, but the fact that a large group of nations 
has united on the metric system, while a small group 
with great commercial interests retains another system, 
makes the attainment of uniformity difficult. 

Substantial agreement as to the use of symbols on 
charts, particularly such as represent aids or dangers 
to navigation, would be desirable and doubtless feasible. 

Privately published charts. Many of the earlier charts 
were prepared and published by private enterprise, and 
such charts are still published, as, for instance, the so- 
called "blue-back" charts printed in London. These 
charts have usually differed from those published by 
the various governments either in representing the main 
features in a very bold manner with little detail or in 
including a considerable area with many plans on a 

Charts and Maps 

single large sheet backed for permanency. An objec- 
tion to the latter is that the durability together with the 
high price tends to keep an old chart in use long after 
it is out of date. It would be financially difficult for 
a private firm to give the service that a government does 
in the matter of correcting the charts and issuing new 
editions, and this is an important consideration in the 
selection of charts. 

Purpose of charts. The main purpose of charts is to 
furnish graphical guides to aid in taking a vessel safely 
from one port to another; they are maps for the use of 
navigators. An experienced mariner may be able to 
steer his vessel over a familiar course without charts, 
but this does not make their publication less necessary. 
Even such an expert pilot doubtless studied the charts 
in the first place; the uncertainties of the sea and 
the changes of information are such that his vessel's 
equipment should include the latest charts, and safety 
requires their examination. The passengers and the 
merchants who intrust their lives or their goods to the 
sea are largely dependent upon the correctness of 
the charts. 

Besides their main purpose charts fill many other 
needs, among which are; for preliminary planning of 
harbor improvements and various engineering works, 
for defensive works and other military uses, for the 
fishing interests, and for general information as to the 
coastal regions. Charts will furnish much of interest 
and instruction to the traveler by sea and the dweller 
near the coast, who will learn to read them. Passenger 
steamers should more often for the interest of their 
patrons display charts of the waters traversed. No 

Requirements for Charts 23 

written or verbal description can give as clear an idea 
of geographical features and relations as a good map 
or chart. 

As the charts are revised from time to time, a com- 
parison of editions at different dates furnishes a record 
of the changes wrought by nature or man, and this is 
especially useful in studying the action in many harbor 
and river entrances, as well as for historical purposes. 

Requirements for charts. As charts are maps of the 
water areas, including the adjoining land, and intended 
primarily for the use of mariners, they differ in impor- 
tant respects from topographic maps or general maps, 
even such as include the water areas. The main 
requirements for charts are these; correct and complete 
information, early publication of new data, clear and 
intelligible representation of the information, conven- 
ient arrangement as navigational instruments, and high 
standard of publication. 

The special and sometimes difficult conditions under 
which charts must be used on shipboard call for good 
judgment throughout their preparation. Even the 
paper on which they are printed is of importance, in 
order that they may be sufficiently durable and suitable 
for plotting. 

Information given on charts. It is evident that it is 
impossible to represent on a chart of any practicable 
scale all the features that exist on the corresponding 
area of the earth's surface. It is essential, therefore, 
that a selection be made of the classes of facts that are 
to be shown, as well as of the detail that is to be used for 
each class. The practical utility of the chart depends 
largely on the good judgment used in this selection. In 

24 Charts and Maps 

the information shown, charts differ from maps prin- 
cipally in representing by soundings and curves the 
configuration of the bottom of the water area, and in 
showing ordinarily the topographic features only in the 
vicinity of the coast line. 

The convenience of mariners should govern in the se- 
lection and arrangement of the information to be shown 
on charts, though they may be made useful for other 
purposes so long as this convenience is not lessened. 
The needs and preferences of navigators alone, how- 
ever, differ so much that a reasonable chart must be 
somewhat of a compromise between conflicting views. 
For certain classes of navigation a boldly drawn chart 
showing only the dangers and a few other soundings 
and some landmarks might be useful. For other 
maritime purposes a more detailed chart would be 
valuable. The first, however, would fail to give facts 
often demanded in the navigational use of the chart, 
and the second if carried to an extreme would make a 
chart difficult to use. 

Shoals and dangers are shown either by the least 
depth or by rock or reef symbols. The characteristic 
soundings are shown on the chart, with abbreviations 
indicating the nature of the bottom. Depth curves 
are drawn, joining together points of like depth, and 
inclosing areas of less depth, on the same principle 
that contours are used on land maps; usually also the 
shoaler spots are made more prominent by sanding 
or tinting the area within them. Lighthouses, buoys, 
and other artificial aids to navigation are represented, 
with descriptive abbreviations. The coast is shown 
by a bold solid line for high water and a dotted line 

Cliffs and Rocky Coast 

Rocky Ledges 

Low Water Line and 
Sa?id Dunes 

Deciduous Trees . 

Pine Trees. 


Curves of equal eleva- 
tion and intermediate 

Salt Marsha 

Coral Ledge covering 
and uncovering 

( fathom curve,shoum thus 

10 and ioo fm. curves, 
shown thus: 

■** -■>■* * 

■K-+ ,- 


TT T Trr^r 

ft 'T Tsl '^ «J1 

Lighthouse _ 

Lighthouse on small 
scale chart — 

Old light tower _ 

Beacon, lighted 

Beacon, not lighted 

Spindle [or stake) ..... 



Rock awash 

Sunken rock — 

Kelp, „ 

No bottom at 30 

Red buoy 

Black buoy 

Horizontally striped 
buoy _ 

striped buoy 

Buoys ivith perch and 


Buoys with perch and 

Lighted buoy 

Mooring buoy 

Landmark, as Cupola, 
Standpipe, etc 

Tide rip _ ._ 

Current, not tidal, in 
kno £s„ 

Current, flood in knots. 

Current, ebb 



Public Road 


Path or Trail 




- — ._■* 






Information Given on Charts 29 

for low water. The main topographic features are 
represented for a moderate distance from the coast, 
with such detail as is useful, depending on the scale of 
the chart. Elevations are given in figures for promi- 
nent summits, islands, and rocks; the general configu- 
ration of hills and mountains is represented by contours 
on large scale charts or by hachures or shading on 
small scale charts. Rivers, streams, lakes, marshes, 
towns, roads, prominent buildings, and other important 
topographic features are shown by appropriate symbols. 
It is important that objects which may be useful in 
navigation as landmarks, whether natural or artificial, 
be plainly shown and described, if necessary to their 
identification, and that they should not be obscured 
by details of lesser importance. On the larger scale 
charts only, vegetation features, particularly areas 
covered by trees, are represented by symbols. The 
land area is usually clearly distinguished from the 
water area by a tint or stipple. Latitude and longitude 
are given by the projection lines and the subdivided 
border, or sometimes on harbor plans by a note giving 
the position of some one point. Brief information as 
to the time and range of the tides is stated in a note. 
Data regarding currents, whether due to tidal or other 
causes, are given by current arrows placed on the chart, 
or by explanatory notes. Compasses are for conven- 
ience printed on the charts, and data given as to the 
magnetic variation and its rate of change. On large 
scale charts scales are provided for use in measuring 
distances. Ranges and channel lines are given when 
required. The ports are indicated where storm warning 
signals are displayed. The areas of forbidden anchor- 

30 Charts and Maps 

ages are shown, and when important, the positions of 
submarine cables. The lines dividing the high seas 
from inland waters are sometimes stated on United 
States charts. Life saving stations are given, and time 
balls are usually noted. Views of important features 
are shown on some charts. 

The layman who looks at the printed chart probably 
does not appreciate the amount or the variety of 
information that must be gathered and sifted and put 
in proper shape for a single chart. 


Need of thorough surveys. As has been stated, a 
good chart requires that a thorough and correct survey 
be first made of the region to be charted. It is said 
that men are very apt to accept as true anything they 
see on a map. As to the nautical chart the mariner 
is likely to be somewhat more critical, however, and 
it is well that he is. The difficulty of charting an 
invisible surface such as the bottom of the sea is great, 
and the proportion of the navigable waters surveyed 
in sufficient detail to be at all certain of the absence of 
uncharted dangers is small. 

The planning of surveys in a new region, such, for 
instance, as the Philippine Islands, presents many 
interesting problems, on the solution of which the 
effectiveness in chart results and the cost of the work 
materially depend. Many local conditions must be 
taken into account. The surveys are made on opposite 
coasts according to the seasonal winds and rainfall. 
In some parts fair-sized steamers are necessary; in 
others launches and small boats can do the work 
more economically. Shore parties with land trans- 
portation are used for portions of the work where the 
country permits. Natives are employed as far as 
practicable for the classes of work they can do; the 
Filipinos, for instance, make good sailors on the vessels 
and excellent penmen in the office. 

The following is a brief outline of the steps of a com- 


Collection of Information 

plete survey for charting purposes, according to the pres- 
ent practice of the United States Coast and Geodetic 
Survey. These are given in their logical order, though 
in actual work this order must often be departed from. 
In this Survey the methods of control have been of a 
high standard; that is, the main stations have been 
accurately determined and permanently marked and 
described, and this has proven an advantage in the 
joining together of the original surveys and resurveys. 

Astronomical observations. To locate on the sur- 
face of the earth the area to be charted, astronomical 
observations are required for the latitude and longitude 
of one or more points. In the best practice the longi- 
tude of a point is obtained by observing the transits 
of stars to get the local time, and sending time signals 
by telegraph to obtain the difference from the local 
time of some other place whose longitude is known. 
The latitude is observed by measuring the difference 
of zenith distance of pairs of stars crossing the meridian 
north and south of the zenith. The azimuth or true 
direction of some line is also obtained from star 
observations, usually by observations with a theodolite 
on a circumpolar star. Much existing chart work 
depends on positions determined by less accurate 
methods, as, for instance, longitudes obtained by trans- 
porting chronometers between the known station and 
that to be determined, or by observations of moon culmi- 
nations, and latitudes obtained by direct observations 
of the altitudes of stars with theodolite or sextant. 

Triangulation. The main framework of the survey 
consists of a series of triangles connecting prominently 
located points which are permanently marked in the 

Cliffy coast line.. 


Villages and toxvns 

Rocky ledges which 
cover and uncover... 

Sand and mud' 
(dry at Low Water) 

Stone bank and beach 
(dry at Low Water) 

*&&& «§#£ 


1 fathom and less 

10 .... 

Rock or Shoal ivhose 
existence is known, but 
the position doubtful 

Reported Rock or 
Shoal whose existance 
is doubtful 

Gaslight Buoys.. 

Bell Buoys. 

Can Buoys, 

Conical Buoys 

Nun Buoys 

;+\P.D. :'5'-P.D. 

W. V.S. Cheq.' 

q. m, <s- 

_ja -* -M 

R. B. H.S. 

W. V.S. Cheq. 
R. B. H.S. 


Coral Reefs 

Spherical Buoys . 

Buoys with Beacons 

Rocks with less than 
6 feet at Low Water 


Spar Buoys 


Rocks awash at Loiv 

%»7 I*. 

(position of) 

Rocks with limiting 
danger line 

Floating Light Vessels. 
(With as many Masts <& 
balls as there are lights, 
forming distinguishing 
marks by day) 

J- *±L. 

Shoal Banks which do 
not uncover, ivhere the 
depth is known 

Anchorage for large 


Anchorage for small 

U Ju 

Overfalls and Tide rips 

(9 (9v§) 

Currents are 
represented by 
Flood tide stream 
Ebb tide stream 






Topography 39 

ground and the location described so that they can be 
found at a future time. At long intervals in the survey 
base lines are laid out and carefully measured with steel 
tape. Signals are erected over the points, including 
those at the ends of the base line, and angles are then 
measured at the various stations. From the measured 
length of the base and the angles the lengths of the 
sides of the triangles are computed, and from these 
lengths and the latitude and longitude of one point the 
latitudes and longitudes of all the other points are 
obtained. When several astronomically determined 
points are connected by such a triangulation a com- 
plication arises from what is known as "deflection 
of the plumb line," which is the angular amount by 
which the actual sea-level surface of the earth departs 
from the symmetrical figure of revolution, owing to the 
variations in the density of the earth's outer layers. 
The distance between two points as measured by trian- 
gulation thus differs from the distance computed from 
the astronomically determined positions. If this irregu- 
larity were not taken care of by adopting mean positions, 
the discrepancy in joining up different surveys would 
in extreme cases amount to about half a mile. 

Survey sheets are next prepared, of suitable size and 
scale. On each sheet a projection is laid down, that is, 
the meridians and parallels are drawn, and all the points 
determined in the triangulation are plotted in their true 
relation. Usually separate sheets are prepared for the 
topography or shore survey and for the hydrography 
or survey of the water area. 

Topography. The topographic survey of the shore 
and as much of the adjacent area as is required is 

40 Collection of Information 

usually made with a plane table, on which the map is 
actually drawn in the field as the work progresses. 
Points are located on the plane table sheet either by 
direct reading of the distance on a stadia rod or by 
intersections from two or more stations. On the plane 
table sheet it is customary to locate the shore or high- 
water line, the low- water line, off-lying rocks, streams, 
rivers, roads, towns, lighthouses, and all prominent 
features near the coast. Elevations are measured with 
the plane table or obtained from the triangulation, and 
are represented on the sheet both by figures and by 
contours, which are lines joining together points of 
the same elevation. For instance, a 100-foot contour 
represents the line where a plane 100 feet above sea 
level would cut the surface of the ground. It is par- 
ticularly important in this topographic work to locate 
accurately objects which are good landmarks and likely 
to be of use to the mariner. In some regions auxiliary 
methods are used in filling in the topography, as, for 
instance, along a difficult coast each feature of impor- 
tance may be located by sextant angles, or a traverse line 
may be run along the shore by the transit and stadia 

The hydrography, or the survey of the water area, is 
of prime importance for the chart, but in the order of 
prosecution of the work it is convenient but not essential 
that it come after sufficient points have been located 
by the triangulation and topography. A hydrographic 
sheet is prepared on which all the points are plotted 
which will be useful. A system of sounding lines is 
then run over the entire area to be surveyed, locating the 
position of the sounding boat at intervals by sextant 




z °$ 




Hydrography 49 

angles on survey signals or by angles from the shore. 
The ordinary method of sounding is to cast a lead from 
a boat and read the depth when the lead touches bottom 
and the line is vertical, and make note of the nature of 
the bottom. There is a systematic spacing between the 
casts of the lead and between the lines passed over by 
the boat, depending on the depth of water and character 
of the bottom. For soundings in deeper water various 
forms of sounding machines are used, with weight 
attached to a wire. For very great depths a small steel 
wire is employed and the weight is detached and left 
on the bottom. The deepest sounding thus far made, 
5269 fathoms, or nearly six miles, was obtained by this 
method in the Pacific Ocean near Guam. 

The offshore soundings are made from a surveying 
steamer; the inshore work is usually done by a launch 
or small boat. 

So far as the navigational use of charts is concerned it 
is important that the hydrography shall show the limit- 
ing depths and the freedom from dangers, of channels, 
entrances, harbors, and anchorages. It is also desirable 
that the soundings shall be carried off shore at least as 
far as the one-hundred -fathom curve, as with the modern 
forms of navigational sounding machines it is possible 
for vessels under way to obtain soundings to this depth, 
and such soundings may be of value in identifying the 
location of the vessel. For depths greater than one 
hundred fathoms the soundings have less direct value 
to navigation except as proving the absence of shoaler 
areas, but soundings throughout the oceanic regions are 
of great geographical interest as well as of direct prac- 
tical value in the laying of cables. 

50 Collection of Information 

It is obvious that the plan of mapping the sea bottom 
by dropping a lead at intervals over its hidden surface 
is far from an ideal one. The lead gives the depth 
only at the point at which it touches the bottom, and 
no information as to the space between the casts except 
such as may be inferred from the relation of successive 
soundings. In numerous cases, after what was con- 
sidered a very thorough survey of a region had been 
made, at some later day a pinnacle rock or other danger 
has been discovered. For instance, a very detailed 
hydrographic survey of Buzzards Bay was made in 
1895; the sounding lines were run at intervals of 50 
to 100 yards, and 91,000 soundings were made for a 
single sheet. Within this area the cruiser Brooklyn 
in 1902 touched a rock which was found to have 18 
feet over it. (Fig. 17.) The least depth in the vicinity 
developed in the original survey was 31 feet. 

For the satisfactory development of hydrographic 
work some invention is much needed which as it 
passes along the bottom will give a continuous depth 
curve. Several devices have successfully accomplished 
this in shoal water, but great credit awaits the in- 
ventor who designs something of more general applica- 

Tides and currents. Information must be obtained 
as to the movement of the water, both vertical and 
horizontal. The rise and fall of the tide are obtained 
by tide gauges, either automatic, which draw a con- 
tinuous tidal curve on a roll of paper, or simple tide 
staffs, which must be read at intervals. The currents, 
whether due to the tides or other movements, are 
measured by noting the movement of partially sub- 

n to tbfl H to $ into $ eO $ St n ft rt (()§$'& ,»$ 

' «* 3 * 1 I f »■ 

<4 n % 76 %<& & ■• 4 2 

■8 **%$% i 8 18 * 

. -icte 



i » ? 




I, » h sbV'2 * 5 



o >- 

> (/) 

X o 

* 1 

oc < 

O ± o 

1- V) - 

O o - 

Q_ o O 

o 3 

. ° (X 

Dragging for Dangers 55 

merged floats. Less accurate but useful information 
as to currents is obtained from the logs of vessels. 

Dragging for dangers has long been resorted to for 
the investigation of isolated spots. A valuable and 
successful means has been employed recently of mak- 
ing sure that an area is free from shoals or rocks 
having less than a certain depth. This is done by 
dragging through the water a wire from 500 to 1400 
feet long, and suspended at the required depth, with 
suitable buoys and weights, and kept taut by the angle 
of pull. If, for instance, the wire is set at a depth of 
30 feet it will indicate the presence of any obstruction 
of less depth by catching on it and upsetting the buoys, 
and such spots are at once marked and investigated. 
Considerable work has been done with such drags in 
the last few years on the Atlantic and Gulf coasts 
and on the Great Lakes. This is of course a somewhat 
tedious process and gives no information as to depths 
greater than that for which the wire is set, but the 
experience already had indicates its great value. It 
will probably be found desirable in time to thus drag all 
water areas important to navigation where the depth 
is near the draft of vessels and the irregular nature of 
the bottom gives indication of dangers. In extensive 
dragging operations near Key West and in Jericho Bay, 
Maine, a number of shoals have been picked up which 
were not found in the original surveys. 

A remarkable instance of the value of the drag was 
the recent discovery of a rock in Blue Hill Bay on the 
coast of Maine. This rock has but 7 feet of water 
over it, and is only 6 feet in diameter at the top. It is 
surrounded by depths of 78 feet, from which it rises 

56 Collection of Information 

nearly perpendicularly. The original survey gave no 
indication of a danger here, and its existence was not 
suspected until it was discovered with the wire drag. 

Another method of dragging that has been employed 
is by means of a pipe suspended beneath a ship's 

Magnetic variation. As the compass is a universal 
navigational instrument, information as to the magnetic 
variation is needed for the charts. The angle between 
the direction of the magnetic needle and the true north 
is measured at various points on both land and sea, 
and at some stations these observations are repeated 
after a number of years. From these results magnetic 
maps are made, from which both the variation and 
its annual change may be taken. 

Reports of dangers. Aside from the more systematic 
surveys as outlined above, much information has 
been placed on the charts from other sources. On 
the earlier charts and on those of more remote regions 
at the present day much of the work has been sketched 
rather than surveyed. Even in the better surveyed 
portions reports come in as to dangers or other matters 
not shown, and if of importance and the report appears 
to be reliable these are sometimes at once put on the 
chart pending further investigation, or in other cases 
an examination is first made. 

Shoals, rocks, and even islands have in numerous 
instances been shown on the charts which no one has 
been able to find again, and many of them after 
repeated searches have been removed. The same 
island or danger has sometimes been charted in two 
or more different positions as reported at various 

Reports of Dangers 57 

times. The treatment of such cases is one of the 
serious and interesting problems of the chart maker. 
It is generally less harmful to show a danger which 
does not exist than to omit one which does exist. On 
the other hand a non-existing danger shown on a chart 
may be the cause of actual expense and loss of time 
in compelling a vessel needlessly to go out of its 

It is surprising to note with what lack of care and of 
sufficient evidence reports of dangers at sea have some- 
times been made, and how incomplete are many of the 
reports even when the existence of the danger is beyond 
question. It is unfortunately true that some of these 
reports are the result of effort to escape blame for acci- 
dent by throwing the fault on the chart. Many such 
reports also result from various illusory appearances. 
A large tree covered with weeds, an overturned iceberg 
strewn with earth and stones, a floating ice-pan covered 
with earth, the swollen carcass of a dead whale, a whale 
with clinging barnacles and seaweed, reflections from 
the clouds, marine animalculse, vegetable growth, scum, 
floating volcanic matter, and partially submerged wrecks 
covered with barnacles, have been mistaken for islands, 
shoals, or reefs. A school of jumping fish has given the 
appearance of breakers or caused a sound like surf, and 
tide rips have been mistaken for breakers. Raper very 
properly calls attention to the obligation upon every 
seaman of carefully investigating doubtful cases and 
making reliable reports. "Of the dangers to which 
navigation is exposed none is more formidable than a 
reef or a shoal in the open sea ; not only from the almost 
certain fate of the ship and her crew that have the 

58 Collection of Information 

misfortune to strike upon it, but also from the anxiety 
with which the navigation of all vessels, within even a 
long distance, must be conducted, on account of the 
uncertainty to which their own reckonings are ever open. 
No commander of a vessel, therefore, who might meet 
unexpectedly with any such danger, could be excused, 
except by urgent circumstances, from taking the neces- 
sary steps both for ascertaining its true position, and for 
giving a description as complete as a prudent regard to 
his own safety allowed." 

As to the older doubtful dangers now shown on the 
oceanic charts, it is estimated that the positions may be 
considered as uncertain by 10 miles in latitude and 
30 miles in longitude, and areas of this extent must be 
searched to determine definitely the question of their 

The following are interesting or typical cases of 
reported dangers: 

The master of an Italian bark in September, 1874, 
reported sighting a large rock in latitude 40° N. and 
longitude 62° 18' W. Fortunately for the charts there 
were two independent reports from other vessels in the 
same month of sighting a partially submerged wreck 
in this vicinity. 

The Spanish steamer Carmen was wrecked in 1891 
by running on a rock off the southwest coast of Leyte; 
the rock was reported to lie one mile off shore, a dan- 
gerous position for vessels using Canigao Channel. A 
survey made in 1903 showed 58 feet of water in this 
location, and that Carmen Rock on which the vessel 
struck was really within one-fourth mile of the beach. 
The rock had, however, for twelve years been shown on 

Reports of Dangers 59 

the charts in a position which made it an obstruction 
to navigation. 

The ship Minerva in 1834 was reported to have 
struck a rock near the middle of the broad entrance to 
Balayan Bay; the fact that this occurred at 2 a.m. 
indicated a very doubtful position, but it was stated 
that an American ship had previously been wrecked on 
the same rock. It consequently appeared as a danger 
on the charts for seventy-one years, when a survey 
showed no depth of less than 190 fathoms in this vicin- 
ity, and it was removed from the charts. 

A British steamer was wrecked in San Bernardino 
Strait in 1905; the master reported that he was in a 
position where the chart showed 51 fathoms, and that 
he was H miles distant from Calantas Rock, and on 
these grounds the finding of the official inquiry was that 
"no blame can be attached to the master, officers, or any 
of the crew for the casualty." Very shortly after the 
disaster, the surveying steamer Pathfinder definitely 
located the wreck and made a survey of the vicinity. 
The previous chart of Calantas Reef was found to be 
fairly correct, and the stranding was determined to have 
occurred well within this reef in a position where the 
chart showed soundings of 31 to 41 fathoms, and 
I mile from Calantas Rock, which rises 5 feet above 
high water. 

A transport entering San Bernardino Strait a few 
years ago ran on a rock and was damaged; the position 
was reported as about two miles southeast of San 
Bernardino Island and near the middle of the passage. 
The rock was not put on the charts, as prompt investi- 
gation showed 50 fathoms of water in this vicinity, and 

60 Collection of Information 

that in all probability the transport actually touched a 
small reef making out from the island. 

The master of the brig Helen reported that his vessel 
was wrecked on a reef lying six miles from Rockall. 
When surveyed Helen Reef was found to be about 
one-third this distance from Rockall. 

An island has been reported in eight different posi- 
tions, ranging in latitude from 30° 29' to 30° 42' N. 
and in longitude from 139° 37' to 140° 38' E. 

There have been a number of reports of islands 
in the area from latitude 40° 00' to 40° 30' N. and longi- 
tude 150° 30' to 151° 00' W. The master of the bark 
Washington reported in 1867: " On my passage 
from the Sandwich Islands to the northwest coast 
of the United States, when in latitude 40° 00' N., in a 
dense fog, I perceived the sea to be discolored. Sound- 
ings at first gave great depths, but diminished gradually 
to 9 fathoms, when through the mist an island was 
seen, along which I sailed 40 miles. It was covered 
with birds, and the sea swarmed with seal and sea 
elephants." A United States vessel searched in this 
vicinity without seeing any indication of land, and 
obtained soundings of 2600 fathoms. A British ship 
in 1858 searched for fourteen days over this area with- 
out finding anything. Searches were also made in 1860 
and 1867 without success, and the present charts 
show no islands in this part of the Pacific. 

In a number of cases erroneous positions have been 
due simply to blunders. Thus Lots Wife, first seen 
by Captain Meares in 1788, was shown on his chart in 
latitude 29° 50' N., longitude 156° 00' E., and stated 
in his book to be in latitude 29° 50' N. and longitude 

Reports of Dangers 61 

142° 23' E. Massachusetts Island by one report was 
in longitude 177° 05' E. and by another in 167° 05' E. 
The apparent blunder of 10° is now immaterial, as the 
island has disappeared from the charts altogether. 
The Knox Islands were placed by the Wilkes Exploring 
Expedition in latitude 5° 59' 15" N., longitude 172° 02' 
33" E. The old British charts showed islands of this 
name also in latitude 5° 59' N., longitude 172° 03' W., 
the longitude being doubtless transposed. In the case 
of Starbuck Island, discovered south of the equator, the 
latitude was apparently transposed, as on old charts 
it was also shown in the position, latitude 5° 40' N., 
longitude 156° 55' W. 

A pinnacle rock can sometimes be located only with 
great difficulty even when known to exist. Rodger 
Rock, on which the bark Ellen struck and was 
damaged, lies in latitude 0° 41/ 15" N. and longitude 
107°31 / E. It has but three feet over it at low tide. The 
British surveying ship Rifleman searched four days 
before finding it, although the plotted tracks showed 
that she and her boats had passed very close to it. 
This indicates that great caution must be used in 
removing a reported danger from the charts. 

The old charts of the Atlantic indicated a danger 
30 to 45 miles to the southwest of Cape St. Vincent. 
This danger was omitted from the charts about 1786 
owing to lack of confirmation. Later, in 1813 and 1821, 
it was reported that vessels were lost or damaged by 
striking this rock. Soundings of over a thousand 
fathoms are now shown on the chart in this vicinity 
and the rock no longer appears. 

A comparison of a Pacific Ocean chart of about 

62 Collection of Information 

forty years ago with one of the present time (Fig. 19) 
illustrates in a striking manner how many doubtful 
dangers, or vigias, have gotten on the charts and how 
after laborious search many of them have now been 
removed. This condition was especially true of the 
Pacific, owing to the numerous reports of an indefinite 
nature from whaling ships, among whose captains 
there was a saying ' '• that they do not care where their 
ship is, so long as there are plenty of whales in sight." 

CHART OF 1869 

P A 









WAKE l.° 





WAKE RK. ?* 






CHART OF 1903 





3002 H \. 
CUREI. .0-^2605 


291 .GA M B,ER tifyT 

2859 »*<■ 

P A C 







¥te. 3211 


2 ? z 13 1817 





2 " z 25 3100 


'WAKE 1. 






























s ft 







Chart schemes. Before commencing the prepara- 
tion of a chart it is necessary to arrange a definite scheme 
for it, and the usefulness of the chart will depend 
materially on this preliminary plan, in which must 
be outlined its scale, size, limits, and features to be 
represented. New charts have sometimes been pre- 
pared simply to fit the surveys as they progressed or 
to fill immediate or local requirements. It is, however, 
desirable that general plans for series or groups of 
charts be made, and with changing needs, information, 
and conditions it is sometimes necessary that existing 
schemes be modified. 

Compilation of information. Considerable work must 
usually be done to get the field records in shape for 
the published chart. The soundings must be plotted 
and the characteristic depths selected. Only a part of 
the soundings that are made can be shown on the 
original sheet and only a small part of these are used on 
the final chart. A selection is made showing the least 
soundings on shoals and bars, the channel depths, and 
the characteristic soundings in anchorages and other 
areas. The original surveys are generally made on a 
considerably larger scale than that on which the chart 
is published, in order that the soundings may be more 
thoroughly plotted. The sheets must then be reduced 
to the scale of publication, and this can conveniently be 
done by means of photography or with a pantograph. 

68 Preparation of Charts 

The best judgment is required in selecting the 
important features to be shown on the chart and 
omitting the less important and not essential features 
which might tend to obscure the others. In charts of 
new regions where complete surveys are lacking, care 
must be exercised in weighing, combining, and adjust- 
ing information from various sources and which is, 
perhaps, more or less conflicting. 

Projections. The surface of the earth being curved, 
there is no possible system of projection by which it can 
be represented on a flat sheet of paper in an ideally 
satisfactory way. Numerous methods of projecting the 
earth's surface upon a plane have been proposed and 
many of them are actually used for various purposes. 
In general each projection has qualities which are 
valuable for certain uses, and deficiencies which make 
it less valuable in other ways. Only four of the different 
projections need be mentioned here as of special 
interest in chart construction. 

Mercator projection. This is a rectangular projection 
in which the meridians are straight lines spaced at equal 
intervals and the parallels are straight lines so spaced 
as to satisfy the condition that a rhumb line, or line on 
the earth cutting successive meridians at the same angle, 
shall appear on the developed projection as a straight 
line preserving the same angle with respect to the 

This projection may be considered as the unrolling 
upon a plane of the surface of a cylinder tangent to the 
earth along the equator, and upon which the various 
features of the earth's surface have been projected in 
such manner as to satisfy the above requirement. 

Mercator Projection 69 

On this projection there is a constant distance be- 
tween the meridians, whereas on the earth they 
actually converge toward the poles. The distance 
between the parallels increases in passing toward the 
poles, approximately in the proportion of the secant 
of the latitude. For each small portion of the map 
the relative proportions are maintained as on the 

Some characteristics of the mercator projection are 
these: The meridians and parallels are all straight lines 
and perpendicular to each other ; there is no convergence 
of the meridians; the minute of longitude is a constant 
distance on the map; the minute of latitude increases in 
length from the equator toward the poles but locally 
retains its true proportion to the minute of longitude ; 
areas and distances increase in scale with the latitude 
so that a given scale is strictly correct only for one 
latitude; great circles and consequently lines of sight 
are curved lines excepting the meridians and the equator ; 
rhumb lines or lines having a constant angle with the 
meridians are straight, and for the same angle are 
parallel in all parts of the chart. These qualities are 
all rigid and the projection can therefore be used for all 
areas, small or large, up to the extent of the earth's 
surface, except that it cannot be extended to the poles, 
as there the length of the minute of latitude would 
become infinite. 

An interesting fact regarding a rhumb line oblique 
to the meridians is that it is a spiral continually 
approaching but never reaching the pole; this spiral 
makes an infinite number of revolutions around the 
pole, and yet it has a finite length for the reason that 

70 Preparation of Charts 

the length of each revolution diminishes as the number 
of revolutions increases. 

The mercator projection has been extensively used 
for nautical charts, for which it presents important 
mechanical advantages, in that adjacent charts can be 
joined on all their edges while still oriented with the 
meridian; all charts are similar; the border may be 
conveniently subdivided, giving a longitude scale appli- 
cable to any part of the chart, but a latitude scale that 
may be used in the same latitude only; courses are 
laid down as straight lines and can be transferred with 
parallel rulers from one part of the chart to another 
without error. On a mercator chart an island in 
latitude 60° would appear four times as large as an 
island of the same actual area at the equator, but 
this distortion of areas, while it gives erroneous impres- 
sions on charts of great extent in latitude, does not seri- 
ously affect the use of the chart for nautical purposes. 
Areas may also be correctly measured on a mercator 
map by taking each projection quadrilateral separately, 
subdividing it if necessary, and using the published 
tables of areas of quadrilaterals in different latitudes. 
Although distance scales vary with the latitude, dis- 
tances can be taken from this chart with fair correctness 
by the use of the latitude border scale for the middle 
latitude, subdividing the total distance if there is much 
range of latitude. The inability to take off the great 
circle or shortest course directly from the mercator 
chart is from a navigational point of view a defect, 
but the most convenient solution for this appears to 
be the supplementary use of a gnomonic chart as will 
be described. The fact that lines of sight are not 




Poly conic Projection 73 

straight lines on this projection is another defect, as 
by the plotting of bearings and angles on approaching 
the land the positions of vessels are located on the 
chart; fortunately, however, the error due to this cause 
usually falls within the other uncertainties involved in 
locating a ship; if need be it would be practicable to 
allow for this curvature. In the polar regions, how- 
ever, the faults of the mercator projection become so 
much exaggerated that it is not used for navigational 
purposes, but because of the absence of commercial 
navigation there this is a minor matter in the general 
question of chart projection. For the plotting of origi- 
nal surveys the mercator projection is not suited and is 
not used, for the reasons above mentioned. 

Tables of "meridional parts" are published which 
give the distance in terms of minutes of longitude from 
the equator to the various parallels; with these tables 
a mercator projection may readily be constructed. 

Airy proposed a graphical method of sweeping the 
arc of a great circle on to a mercator chart, and tables 
are published for this purpose. The method is only 
approximate and is limited in application, and the 
supplementary use of a gnomonic chart would appear 
to be preferable. 

Polyconic projection. In plotting the original surveys 
it is essential that a projection be used which will for the 
area included on a survey sheet show the points in their 
correct relation both as to direction and distance. 
These conditions are substantially fulfilled by several 
projections, of which the polyconic is used in the 
United States. If a hollow cone were placed so that 
it would either be tangent to the earth's surface along 

74 Preparation of Charts 

one of the parallels of latitude or cut it along two 
parallels, and the points projected on to this cone, and 
the cone then unrolled and laid out flat, the result 
would be a conical projection, of which there are several 
variations. If successive tangent cones be used and 
each parallel of latitude be developed as the circum- 
ference of the base of a right cone tangent to the spheroid 
along that parallel, the result is the polyconic projection, 
which has been used for field sheets and for the large 
scale charts, as well as for the topographic maps of the 
United States. This projection has valuable qualities 
for moderate areas of the earth's surface, within which 
the scale is approximately uniform, areas retain nearly 
their true proportions, and great circles and conse- 
quently all bearings and directions are approximately 
straight lines. The parallels of latitude are arcs of 
circles with radiuses increasing as we recede from the 
pole; therefore they are not truly parallel and the length 
of the degree of latitude increases either side from the 
central meridian. The meridians converge toward the 
poles and become slightly curved as we recede from 
the central one; the longitude scale is everywhere correct, 
but the latitude scale is strictly correct only on the 
central meridian. The angles of intersection of parallels 
and meridians are right angles or nearly so. The 
polyconic projection is not used for very extensive areas 
of the earth's surface, as for instance a hemisphere. 

Gnomonic projection. In this projection the eye is 
assumed to be at the center of the earth and the features 
are projected upon a plane tangent to some point on 
the earth's surface. It is practicable to use this projec- 
tion for oceanic areas, and it has the very important 

o o 

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;0' Long, $l) y Eaat <y>° from 190 'fcreen."!^, 



Arbitrary Projection 79 

quality that every straight line on it represents a great 
circle of the earth. To obtain the great circle or 
shortest course between two points it is therefore only 
necessary to draw a straight line between the points 
on a gnomonic chart. Because of the great distortion 
near the edges this projection is not otherwise adapted 
to navigational use, and it is employed only to mark 
out the general course, and sufficient points are then 
transferred to a mercator chart. The gnomonic chart 
is therefore useful in supplementing the mercator chart, 
supplying its deficiencies as to convenience in marking 
out great circle courses. The great circle course can 
be derived not only more easily and quickly from the 
gnomonic chart than by computation, but the chart is 
also to be preferred because the course marked out on 
it will show at once if any obstruction, as an island or 
danger, is met or too high a latitude is reached. A 
modified or composite course can readily be laid out 
on a gnomonic chart. 

Arbitrary projection. The few charts published of 
the polar regions are sometimes on an arbitrary pro- 
jection, in which the meridians are straight lines radiat- 
ing from the pole and the parallels are equidistant 
circles with the pole as center. The latitude scale is 
uniform. At some distance from the pole the longitude 
scale becomes very much distorted, but the projection 
is a practicable and convenient one for the immediate 
polar regions. Gnomonic and conical projections are 
also used for the polar charts, differing little from the 
foregoing for moderate areas. 

Scales. Charts are published on a variety of scales 
to suit different needs of navigation, and the usual 

80 Preparation of Charts 

classification depends on scale. In addition to the 
ocean charts covering a single ocean in either one or 
several sheets and intended for navigation on the high 
seas, there are for our Atlantic coast the following series ; 

Sailing charts, scale about TTo~o Foo~> ^ or general coast- 
wise navigation. 

General coast charts, scale 4 J , for local coastwise 

Coast charts, scale 80 1 00 , for approaching the coast 
at any point and for inside passages. 

Harbor and channel charts, of various large scales 
from 5-^00" t° 60000 ' ^ or entering harbors and rivers and 
passing through channels. 

The expression of scales by miles to the inch or inches 
to the mile is the more familiar. The expression of 
scale in the manner used by the Coast Survey and by 
most of the European countries, by standard fractions 
as 8Q i , meaning that any distance on the chart is 
80 o 00 of the actual distance on the earth, has some 
advantages. For instance, the relation of these frac- 
tions gives at a glance the relation of the scales of the 
charts. Thus a g- o 00 chart is on a scale five times as 
large as a 400000 cnart. 

For the more important harbors charts have been 
published on several different scales to meet various 
needs. Thus New York Harbor is shown on charts of 

scales 01 ! o' 4 c so oo» 200000* 400000 an0 - 
T2~o oToo"' eacn °f course including a different area. 

The selection of suitable publication scales is of 
prime importance; a large scale permits of greater 
clearness and of showing more detail, but on the other 
hand restricts the area and the points that can be shown 


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Nautical Mile 




Scales 83 

on a single sheet, or else makes a chart of excessive 
dimensions. In general in chart preparation the scale 
should be restricted to the minimum that can be used 
to fulfill the particular object and clearly represent 
what is desired. A chart of very large scale is not 
convenient for plotting, and a moving vessel may pass 
quickly beyond it or into range of objects beyond the 
limits of the chart. 


Methods of publication. An ideal process of publi- 
cation for nautical charts would include the follow- 
ing features; rapidity in getting out new charts, facility 
in reprinting and correcting existing charts, clearness 
and sharpness of print, durability of paper and print, 
and correctness of scale. It is difficult to fulfill all these 
requirements by any method as yet developed. In the 
Coast and Geodetic Survey several different processes 
are in use at present; charts are engraved on copper 
and printed directly from the copper plate, or they are 
transferred from the copper plate to stone and printed 
from the stone, or a finished drawing is made and 
transferred to stone by photolithography and printed 
from the stone, or an etching is made on copper from a 
finished drawing and printed from a transfer to stone. 
Charts in other countries are in large part printed from 
engraved plates, excepting some preliminary charts by 

Copper plate engraving and printing have long been 
used in chart preparation. A drawing is prepared as 
a guide for the engraver; this must be correct as to all 
information to be shown but need not be a finished 
drawing. A true projection is ruled upon a copper 
plate. By photography a matrix is made from the 
drawing and a wax impression taken from this matrix. 
This is then laid down on the copper to fit the projection, 
and the impression is chemically fixed on to the copper. 





Copper Plate 89 

The work thus marked out is engraved by hand or by 
machine. A high degree of skill is required in the 
accuracy and finish necessary for chart engraving. 
Machines have been invented in recent years which can 
be used for portions of the work on copper plates, as 
for instance for cutting the sounding figures, the 
bottom characteristics, the border and projection lines, 
border divisions, compasses, line ruling, and stipple 
ruling. Stamps and dies have been successfully used 
for some symbols and notes, and roulettes for shading. 
By means of these various machines, many of which are 
American inventions, the process of chart publication 
from plates has been materially facilitated. 

When the plate is completed an alto, or raised copy, 
is made by depositing copper on to it in an electrotype 
vat, and from this alto another basso or sunken copy is 
made by the same process. This latter basso is used 
in printing. A copper plate may be used for about 
3000 impressions, after which it may become too much 
worn for satisfactory chart printing. By printing from 
a duplicate basso the original plate is preserved and 
additional copies can be made when needed. The 
use of the alto also greatly facilitates matters when a 
considerable correction to the chart is required. All 
the portions of the chart to be changed can be scraped 
off the alto, and when a new basso is electro typed from 
this scraped alto all such areas will of course appear 
as smooth copper, on which the new work can be 
engraved. Numerous small corrections are called for 
on charts, and on copper plates where these are to 
replace old work the latter is removed either by ham- 
mering up the back of the plate or by scraping its face. 

90 Publication of Charts 

Printing directly from plates is a laborious process. 
After the press bed has been carefully padded to take 
up inequalities in the plate, the surface of the latter 
is covered with ink and then carefully wiped off by 
hand, leaving the ink only in the engraved lines. The 
paper, first dampened, is laid on the plate, and passes 
with it beneath the cylinder of the press under consider- 
able pressure. The prints are calendered by being 
placed in a hydraulic press under 600 tons pressure. 
The charts are beautifully clear and sharp, not equalled 
by other methods of printing. Owing to the wetting 
and drying of the paper, the finished print is, however, 
quite appreciably smaller in scale than the plate, and 
the shrinkage is greater in one direction than in the 
other. The average day's work for one press and two 
men is 75 prints. This is small compared with the 
output practicable with lithographic presses. On the 
other hand a plate can be prepared for printing more 
readily than a lithographic stone. For small editions 
the plate printing compares well in economy with 
lithographic printing, and the plate can also be printed 
on short notice. Because of changes in aids to naviga- 
tion and other corrections, it is usually desirable to 
print at one time only a sufficient number of copies 
of a chart to meet current demands, and not to carry 
a large stock on hand. 

The copper plates, bassos, and altos make a very 
convenient and enduring means of preserving the 
chart ready for printing or for further correction. A 
large number of plates can be placed in a small space, 
and if properly cared for they may be stored indefinitely 
without deterioration. 




Photolithography 93 

With plate printing it is not practicable to print 
rnore than one impression on the chart or to use more 
than one color, and plate-printed charts are therefore 
in black only. 

Engraving on stone. On the United States Lake 
Survey the charts are first engraved on stone, and by 
a special process the work is then transferred to small 
copper plates, which are preserved. The final publi- 
cation is by lithography, transferring again from the 
plates to stone. 

Photolithography is a quick method of publishing 
a chart. It would be practicable by this means to 
reproduce the original survey sheets, but ordinarily 
these are not suitable as to scale and legibility, and 
it is necessary to make a new drawing, usually on 
tracing vellum. This is photographed on to glass 
plates, on the scale of the proposed chart. From these 
glass negatives positive prints are made on sensitized 
lithographic paper. These prints are fitted together 
and then inked, taking the ink only where the lines 
appear. This transfer print is then laid face down 
on the lithographic stone and run through a press 
under pressure, the stone absorbing the ink from the 
paper. The stone is then treated so that the inked 
portion remains slightly raised, and from this stone an 
indefinite number of charts can be printed in a litho- 
graphic press at the rate of 1000 an hour. The paper 
is not moistened, and consequently there is little distor- 
tion or change of scale in prints from stone. If desired 
to shade the land or use another color for any other 
purpose, additional impressions can be made on the 
same charts from other stones. Because of the bulk 

94 Publication of Charts 

of the stones, work cannot ordinarily be retained on 
them, but the chart is cleaned off and the stones 
repeatedly used until worn thin. The original dra wing- 
as well as the negatives is preserved, from which the 
chart can again be published. For republication, the 
process is, however, not entirely satisfactory; the 
negatives are not always permanent, the work must 
again be assembled and transferred to the stone, 
changes or corrections are not very conveniently made 
on either drawing or negative, and after repeated 
changes the drawing becomes difficult to use in 
photolithography. Whether the charts are actually 
printed from copper or stone, there are decided advan- 
tages therefore in the matter of correction work and 
future editions in having the charts engraved on copper. 
On the other hand, the advantages of the photolitho- 
graphic process are the ability to publish new drawings 
promptly, to use more than one shade on a chart, to 
obtain prints with little change of scale or distortion, 
and to print large editions rapidly. 

Lithographic printing by transfer from engraved 
plates. An impression on transfer paper may be taken 
from an engraved plate and this laid down on the stone 
in a manner similar to that used in laying down the 
prints from the glass negatives in photolithography. 
Prints are then made from the stone the same as 
in photolithography, but with superior results as to 
clearness. This general process is extensively used 
in both map and chart publishing in this country, as 
it combines the advantages of the plate in preservation 
of the chart record and facility of correction, and the 
advantages of the lithographic printing in less distortion 

Etching on Copper 95 

of the printed chart, ability to print more than one shade, 
and facility for large editions. As the transfer from 
the plate can be readily made it is also better applicable 
to small editions than is photolithography. It is, how- 
ever, not as convenient in the latter respect as plate 
printing, and it does not give a resulting impression 
equal in clearness or durability to the impression directly 
from the plate. 

Etching on copper for chart publication has been 
recently developed in the Coast and Geodetic Survey. 
A finished tracing is made, the surface of a smooth cop- 
per plate is sensitized, and by exposure to the sun a 
print is made on the sensitized surface. It is essential 
to use an air-exhausted printing frame so as to get 
good contact between the vellum and the plate. The 
work is then etched into the copper and the plate 
cleaned and touched up, after which it may be used the 
same as a hand-engraved plate, either for transfer to 
stone or direct plate printing. The expense and time 
required in the etching process are much less than for 
hand engraving. The process has been successfully used 
for a number of harbor charts. The etching of course 
will be of the same scale as the vellum at the time of 
the print, and vellum varies somewhat in scale with 
weather conditions and age. Unless overcome by the 
substitution of some more invariable material in place 
of vellum, this might be an obstacle to the use of the 
process for general charts where a true scale on the 
copper plate is desirable because of future work to be 
done on the plate. It must also be taken into account 
that the etching requires a finished tracing in ink, which 
is not essential for the hand engraver; if, however, 

96 Publication of Charts 

the chart is first published by photolithography, as is the 
usual practice in the Coast and Geodetic Survey, the 
same tracing is used for both processes. 

Distribution of charts. Charts published by the 
government are sold to the public at a small price, 
estimated to cover the cost of paper and printing. The 
charts may be obtained direct from the publishing 
office or from the chart agents who are to be found in 
all the principal seaports. Catalogues are published 
from time to time giving complete lists of the current 
charts and the main facts regarding them. Index maps 
show graphically the area covered by each chart. The 
notices to mariners contain announcement of new charts 
or new editions published and of charts or editions 
cancelled, as well as of all corrections. 


Need for revision. The making of the survey and the 
printing of the chart do not complete the problem of the 
chart maker. Both nature and man are constantly 
changing the facts the representation of which has been 
attempted on the charts, and also the needs of man are 
always varying. The original surveys are made to 
meet the reasonable requirements of the time, but 
breakwaters and jetties are built, and channels and 
harbors dredged and otherwise improved, and cities 
built, and new paths of commerce are opened which 
bring vessels into waters previously thought of minor 

With the increase of commerce and speed of vessels 
more direct routes are demanded for reasons of econ- 
omy. Inside routes not originally used are sometimes 
developed for defensive reasons. The average draft of 
the larger vessels has also increased remarkably since 
the modern hydrographic surveys were commenced, 
and surveys once made to insure safety for the deepest 
vessels of that time are now not adequate. The average 
loaded draft of the 20 largest steamships of the world 
has increased as follows: 1848, 19 feet; 1873, 24 feet; 
1898, 29 feet; 1903, 32 feet. The average length of 
these vessels was 230 feet in 1848, 390 feet in 1873, 
541 feet in 1898, and 640 feet in 1903. The number of 
vessels drawing as much as 26|- feet rose from 36 in 
1902 to 185 in 1904. In 1906 there were 17 vessels 

98 Correction of Charts 

afloat, drawing 32 feet and upwards. There are now 
two steamers on the Atlantic 790 feet long, 88 feet beam, 
and 37^ feet draft when fully loaded, and larger vessels 
are already planned. 

Great natural agencies are also constantly at work 
effecting changes in features shown on the charts. 
The action of currents and waves is continually cutting 
away or building the shore, particularly on sandy 
coasts exposed to storms. When surveyed in 1849 
Fishing Point on the east coast of Maryland was but 
a bend in the shore line. By 1887 it had built out 
about two miles in a southerly direction, and in 1902 
about two-thirds of a mile further, curving to the west- 
ward. Altogether in about half a century this tongue 
of land has grown out nearly three miles. 

Rivers are bearing vast quantities of sediment and 
depositing these near their mouths, pushing out the 
coast line and filling in the bottom. The main mouths 
of the Mississippi are advancing into the Gulf, but at 
a comparatively slow rate. A break from the main 
river at Cubit's Gap just above the head of the passes, 
however, has done an enormous amount of land 
making, filling in an area of about 50 square miles 
between 1852 and 1905. 

The mouth of the Columbia River in Oregon shows 
an interesting example of the movement of an island. 
The chart of 1851 shows the center of Sand Island 
3j miles southeast of Cape Disappointment, the chart 
of 1870 shows it 2f miles southeast, and the chart 
of 1905 shows it \\ miles easterly. This island has 
thus moved 2 miles northwesterly directly across the 
middle of the river entrance, closing up the former 

Nautical Miles 







\ \ o foot curve — 

\ \ i2 " " 



*° 1890 


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Nautical Mile 

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NewBogoslof JAGGAR 1907 




Need for Revision 109 

north channel. The southern point of the entrance, 
Clatsop Spit, has built out about the same distance. 

Volcanic action in well authenticated cases has 
caused islands to rise or disappear. In the present 
location of Bogoslof Island in Bering Sea the early 
voyagers described a "sail rock." In this position in 
1796 there arose a high island. In 1883 another island 
appeared near it. In 1906 a high cone arose between 
the two, and a continuous island was formed over 
lijr miles long and 500 feet high. The latest report 
(September, 1907) was that this central peak had sud- 
denly collapsed and disappeared. Bogoslof is an active 
volcano, and the main changes have been the result 
of violent volcanic action. The history of this island 
for over a century past forms a remarkable record of 
violent transformations in the sea. 

Earthquakes sometimes cause sudden displacements, 
horizontal or vertical, of sufficient amount to affect the 
information shown on the charts. A careful investiga- 
tion of the effects of the earthquake in Yakutat Bay, 
Alaska, in September, 1899, showed that the shore 
was raised in some parts with a maximum uplift 
of 47 feet and depressed in other parts, and that at 
least two reefs and four islets were raised in the water 
area where none appeared before. Undoubtedly there 
were changes in the water depths, but definite informa- 
tion is lacking because there had been no previous 
hydrographic survey. The San Francisco earthquake 
of 1906 caused little vertical displacement, but there 
were horizontal changes of relative position as much 
as 16 feet; so far as known this earthquake did not 
affect the practical accuracy of the charts. Related 

110 Correction of Charts 

to earthquake phenomena are the gradual coast move- 
ments of elevation or subsidence which are taking 
place but at so slow a rate as not to sensibly affect the 
charts in ordinary intervals of time. 

Another agency at work is the coral polyp on the 
coral reefs; although the rate of growth appears to be 
very slow, the resulting reefs and keys are an important 
feature in tropical seas. 

Practically all of the land features shown on charts 
are likewise subject to changes, the more rapid of 
which are mainly due to the works of man. 

The changes of channels and of commercial needs 
cause many alterations to be made from time to time 
in the lights and buoys which are shown on the charts. 

Methods of correction. The problem of keeping a 
chart sufficiently up to date is one of much practical 
importance and one which must be taken into account 
in planning what should be shown on the chart in the 
first place so as to bring it within the range of practi- 
cable revision. 

Certain features are corrected at once on the charts 
as soon as the information is received, such as dangers 
reported, and changes in lights and buoys. Where 
harbor works are in progress the periodic surveys made 
in this country by the Corps of Engineers furnish data 
which are applied promptly to the charts. Reported 
dangers in channels and bars are investigated by spe- 
cial surveys and the information is put on the charts. 
Examinations are made from time to time for the 
revision of the features along the coast line. Complete 
resurveys have been made, at long intervals, of some 
important portions of the coast where there has been 

Methods of Correction 111 

evidence of change, and these, when they become 
available, are applied to the charts. All parts of the 
coast where the exposed portions are not of very 
permanent material will require resurveys at intervals, 
depending on their importance and the rate of change. 

Notwithstanding the great progress made in hydro- 
graphic surveys, a considerable number of rocks and 
shoals dangerous to navigation and not previously 
shown on the charts are reported, averaging nearly 400 
each year for the last six years, according to the British 
reports. Of the 367 reported in 1906, 11 were discov- 
ered by vessels striking them. 

Immediate information in the form of Notices to 
Mariners is published, of the more important corrections 
to charts which can be made by hand. These correc- 
tions show what charts are affected, and give sufficient 
data for plotting. 

In the case of extensive corrections or new surveys 
a new edition of the chart is printed and all existing 
copies of the previous edition are canceled. 

It is important that the user of the chart shall make 
certain that he has the latest edition and that all correc- 
tions from its date of issue have been applied from the 
Notices to Mariners. 

It is unfortunately true that owing to failure to take 
proper account of the notices, or to economy, old 
editions or uncorrected charts are sometimes used, and 
in a number of cases the loss of vessels has been directly 
due to this cause. Those responsible for the safe 
navigation of vessels should insist that the latest editions 
of charts are provided and that all charts to be used are 
inspected and corrected to date. 


Reading charts. A chart is a representation on paper 
of hydrographic and topographic information by means 
of various conventional methods and symbols. It is 
evidently important for those making use of charts 
to understand the system and conventions used, and 
to be able to interpret readily the various parts of 
the chart. The ability to read a chart must include 
an understanding of all its features, such as scale, 
projection, geographic position, directions, depths, 
plane of reference, aids to navigation, tides, cur- 
rents, elevations, topography, and date of survey and 

Scale. For American and British charts the scale is 
usually expressed by the inches or fractions of an inch 
to the minute or degree of latitude, or by the fractional 
proportion of a distance on the map to the correspond- 
ing distance on the earth. These fractions are some- 
times stated on the British charts, and nearly always 
on those of the United States Coast Survey. The chart 
catalogues give the scale in one or the other form. A 
familiarity with the meaning of scales is of value in 
selecting the most suitable chart, in judging of the 
relative uses of charts, and in estimating distances. 
Where the fractional scales are stated they furnish a 
simple means of comparing charts, as, for instance, a 
chart on Tjfhnr scale will show all distances just twice 
as long as a chart on tooVoo scale. 


Scale 113 

The following are scale equivalents: 

Scale toio o is equivalent to 7.30 inches to one nautical mile. 

Scale 20000 is equivalent to 3.65 inches to one nautical mile. 

Scale 4o<too is equivalent to 1.82 inches to one nautical mile. 

Scale soioo is equivalent to 1.46 inches to one nautical mile. 

Scale soiroo is equivalent to 0.91 inch to one nautical mile. 

Scale tooWo is equivalent to 0.73 inch to one nautical mile. 

Scale uooVoo is equivalent to 0.36 inch to one nautical mile. 

Scale 400V00 is equivalent to 0.18 inch to one nautical mile. 

Scale to oIjoo o is equivalent to 0.07 inch to one nautical mile. 

Scale Tiolooo is equivalent to 0.06 inch to one nautical mile. 

For use in measuring distances on large scale charts 
the length of one or more nautical miles is usually 
drawn on the chart, and sometimes scales are also given 
in other units. On British charts the nautical mile 
scale is divided into tenths (that is, cables of 100 fathoms 
or 600 feet length) ; on the American charts into quarters 
and eighths. Where the scale covers more than one 
mile the fractional divisions are shown only for the left- 
hand mile and the zero of the scale is placed between this 
and the full mile scale, so that with dividers the full 
miles and fraction may readily be taken off. The 
nautical mile in the United States is taken to be the 
length of a minute of arc of a great circle on a sphere 
whose surface equals that of the earth; this definition 
makes the nautical mile equal 6080.27 feet. Lecky 
adopts 6080 feet as the nautical mile. The length of 
the actual minute of latitude on the earth's surface 
increases from 6046 feet at the equator to 6108 feet at 
the poles, an increase of about one per cent. It is, 
however, this somewhat variable unit of length which 

114 Reading Charts 

is ordinarily used in scaling distances on the sailing 

On small scale charts there is usually a border scale 
entirely around the chart, conveniently subdivided; this 
serves the double purpose of facilitating the plotting or 
reading of positions by latitude and longitude and of 
furnishing a scale of minutes of latitude for use in 
measuring distances. On a mercator chart this scale of 
course varies with the latitude and it must be referred 
to in the mean latitude of the distance to be measured. 
In general practice the minute of latitude is taken as 
equal to the nautical mile. 

Projection. On only a few charts is there a statement 
of the projection used. Practically all general sailing 
charts are on the mercator projection, which can be 
readily recognized by the rectangular network of meridi- 
ans and parallels and the increase with latitude of the 
distance between the parallels. On large scale local 
and harbor charts the kind of projection used is not of 
importance to navigation, as for such limited areas 
the difference between projections would not affect the 
use of the chart. On certain small scale charts of the 
United States Court Survey which are on the poly conic 
projection this fact is stated on the chart, and can also 
be readily recognized by the convergence of the meridi- 
ans and curvature of the parallels. Gnomonic charts 
intended for taking off great circle courses are always 
described in their titles and are also easily recognized 
by the increased scale and distortion toward all the 
borders. Charts of the polar regions are published 
on several different projections, which are distinguished 
from the mercator by their circular or curved parallels. 

Geographic Position 115 

Geographic position. For large scale and harbor 
charts the latitude and longitude of some point marked 
on the chart are sometimes stated on the face of the 
chart. For others of these, however, and for smaller 
scale and general charts, positions are obtained by 
reference to the border scale. There is a latitude 
scale down either side of the chart, and a longitude 
scale across the top and bottom. These scales are 
conveniently subdivided into degrees, minutes, or 
fractions of a minute. The minute is divided into 
tenths (6"), sixths (10"), quarters (15"), or halves 
(30") on various charts. 

Directions are indicated on charts both by the projec- 
tion lines and by compass roses. Nearly all charts are 
now oriented with the meridian, that is, north is the 
top of the chart, and on a mercator chart the east and 
west border lines are parallel with the meridians and 
the north and south border lines with the parallels. 
Formerly many charts were not so oriented. Some 
of these are still in use and can readily be recog- 
nized by the diagonal or inclined direction of the 
projection lines with respect to the border of the chart. 
Of course directions must not be referred to the border 
lines of these diagonal charts, and scales along such 
border lines must not be used. Directions with respect 
to true north may always be referred to the projection 
lines of the chart, but on a polyconic or polar chart 
a direction must not be carried so far from any projec- 
tion line as to introduce error on account of convergence 
of the meridians. Compass roses are placed on charts 
to facilitate the taking off or laying down of directions, 
though in some respects their use is less accurate and 

116 Reading Charts 

convenient than the use of protractors, referring to 
the projection lines. The British charts and many of 
those of the United States Coast Survey have only 
magnetic compasses, with degrees outside and points 
inside, the former graduated to 90°. These are engraved 
on the chart with the magnetic variation for the date 
of publication, or for a few years in advance, and give 
the annual change in the variation. Because of expense 
of engraving they can be changed on the charts only 
at intervals of some years, and until this is done allow- 
ance for the change in variation is to be made if 
important. The German charts and those of the 
United States Hydrographic Office now have a three- 
fold compass, the outer one degrees true, the middle 
degrees magnetic and the inner points magnetic; the 
degrees in both cases are graduated to 360°, reading 
from north through east, south, and west; thus north- 
west would be stated as 315° instead of N. 45° W. 
Small scale charts covering extensive areas have no 
magnetic compasses. They sometimes have true com- 
passes, and usually have the isogonic lines, or lines of 
equal magnetic variation, marked on them, from which 
the variation at any intermediate point can be estimated. 

Depths. The unit used for depths is always stated 
plainly on the chart, and it is important to note this 
carefully, as the British, American, and Japanese charts 
use fathoms for some charts and feet for others, and 
most other countries use meters. Some of the earlier 
charts of the United States coast have the depths inside 
of the 18-foot curve in feet and outside of that curve in 

Depth curves are shown on charts in order to bring 

Depths 117 

clearly to the eye the different depth areas and the 
limits for navigation of vessels of various drafts. The 
shoaler areas are usually indicated by sanding the outer 
limit or the entire area within the depth curve. For 
the curves of greater depths various standard symbols 
are used which vary slightly in the different series 
but which may readily be recognized by the soundings 
on either side of them. On the British charts the 
1 and 3 fathom curves are usually indicated by sanding 
the outer edge of the areas of these depths respectively ; 
beyond these the standard curves shown on these 
charts are the 5, 10, 20, and 100 fathom curves. Similar 
curves are used on the United States charts. The 
German charts show the 2, 4, 6, 10, and 20 meter and 
various deeper curves, and the French the 2, 5, 10, and 
20 meter and deeper curves. On the United States 
Lake Survey charts the areas included within the 6, 12, 
and 18 foot curves are shaded with a blue tint, heavy 
along the outer edge, which brings out strongly the 
shoal areas. 

Depth curves if clearly shown are a great aid in inter- 
preting the hydrography and making plain the shoals 
and passages. The system of curves should always be 
understood when using a chart, and it may sometimes 
aid the navigator to trace out with a pencil an additional 
curve, if needed, beyond the draft of his vessel. The 
abbreviations used for the bottom characteristics are 
explained either on the chart or on the sheet of chart 
symbols, and give information which is useful in 
anchoring, and may be helpful in identifying a position 
by soundings. When a sounding is made without the 
lead reaching bottom, the depth obtained is sometimes 

118 Reading Charts 

shown on the chart by a short line and zero above the 
figure, indicating that at the depth stated, bottom was 
not obtained (no bottom). There are a few important 
symbols shown in the water area of charts. The 
sunken rock symbol indicates a dangerous area, or a 
danger having a moderate depth of water over it, or a 
rock the least water over which is not known ; ordinarily 
on the United States charts the least depth will be stated 
when known, and the symbol omitted. The rock 
awash symbol indicates a rock awash at some stage of 
the tide, unless more definitely stated. The position 
of a wreck is indicated by a special symbol. P. D. 
(position doubtful) and E. D. (existence doubtful) are 
placed after soundings or rocks or other features which 
depend on some doubtful report not yet verified. 

The following are the relations between depth units 
found on various charts: 

1 meter = 3.281 English feet =0.547 English fathoms. 

1 sajene (Russian) = 7 English feet =1.167 English fathoms. 
1 braza(old Spanish) = 5.484 English feet =0.914 English fathom. 
1.829 meters = 6 English feet =1.000 English fathom. 

Aids to navigation. Each series of charts has a 
definite system of representing the aids to navigation; 
these are similar in principle but differ as to detail. The 
characteristics of the lights, light-vessels, buoys, and 
beacons are usually explained by abbreviations placed 
by the side of each, and the entire system of representa- 
tion is given on the explanatory sheet for the charts. 
Various methods of coloring lights and sectors and 
buoys are in use on different charts. It is evidently of 
importance that the user of the chart should readily 

Plane of Reference 119 

understand the significance of the navigational aids as 
shown. For details regarding lights it is of course 
desirable to refer to the light lists; for the coasts of the 
United States detailed buoy lists are also published. 
Range and channel lines when shown are represented 
by distinctive symbols with bearings indicated. Danger 
ranges for the avoidance of shoals are sometimes shown. 
On the British charts bearings as stated on range and 
channel lines are magnetic; the custom varies on other 
charts and must be carefully noted in each case. 

Plane of reference. The soundings given on the 
chart express the depth of water when the tide is at the 
height adopted for the plane of reference; this same 
plane is used in the tide tables, which thus will indicate 
the amount to be added to the soundings when the tide 
is above the plane, or to be subtracted when it is below. 
In order to be on the safe side the plane of reference 
adopted is always some low stage of the tide, so that 
there is usually more water than shown on the chart. 

On the British and German charts the soundings are 
reduced to the mean low water of ordinary spring tides, 
unless otherwise stated. On the charts of the Coast 
and Geodetic Survey the following are the planes of 
reference: for the Atlantic and Gulf coasts, the mean 
of the low waters ; for the Pacific coast, Alaska, and the 
Philippines, the mean of the lower low waters, except 
for Puget Sound and Wrangell Narrows, where planes 
two and three feet lower respectively have been adopted. 
According to the Tide Tables for 1908, at New York 
(Sandy Hook) the tide will fall below the plane of 
reference on 135 days during the year, but the extreme 
low tide will be only one foot below the plane. At 

120 Reading Charts 

Portland, Maine, in 1908, the extreme low water is 2.1 
feet below the plane, and at San Francisco 1.5 feet. Of 
course when the tide is below the plane of reference the 
amount must be subtracted from the depths shown on 
the chart. 

Strong winds and unusual barometric pressure may 
have a marked effect on the height of tide, so that it may 
differ appreciably from the predicted height, which is of 
course based on normal conditions. At Baltimore and 
at Willets Point observation shows that a heavy wind 
may reduce the tide four feet below the predicted heights. 

Tides. Information regarding tides is given on all 
large scale charts, and additional information and pre- 
dictions may be found in the Tide Tables. On the 
charts of the United States coast there is a small tide 
table giving for the high and low waters the time rela- 
tions to the moon's transit and the height relations to 
the plane of reference. On the British charts there is 
a brief statement as to the tides either at the port on 
the chart or in the general notes ; this ordinarily gives 
the interval in hours and minutes between the moon's 
meridian passage and the time of high water for the 
periods of full and new moon, and also the amount in 
feet that the spring and neap tides rise above the plane 
of reference, and the range of the neap tide. The 
following is an example of such a tide note: " H. W. P. 
and C. Campbellton IV h m . Springs rise 10 feet, 
Neaps 7 feet." 

At some important ports information as to the state 
of the tide is given to vessels, either by means of signal 
balls, or by automatic tidal indicators, as at the Narrows 
in New York Harbor, where a large dial shows to 

Currents 121 

passing vessels the height of the tide, and an arrow 
indicates whether it is rising or falling. 

The tidal information becomes important and must 
be considered in navigation or in anchoring in waters 
where the available depth at low water approximates 
the draft of the vessel. In the general use of coast 
charts it is also important to observe the effect of the 
stage of tide on the appearance of many features. 
Rocks rising some feet above low water may be entirely 
submerged at high water. In some areas the aspect 
may be radically changed between high and low water 
by the baring of extensive shoals or reefs. 

Currents. Information, when available, as to cur- 
rents is given either by a note or by current arrows 
placed on the chart at the position of observation. 
Additional information as to certain regions is given 
in the United States Tide Tables. Tidal currents, 
flood and ebb, and currents not due to tidal action are 
distinguished by symbols, and the velocity is given 
in knots, and on some charts is indicated by the lengths 
of the arrows. 

Complete and systematic current observations have 
been made in comparatively few localities because of 
the time and expense necessary to get the full informa- 
tion as to the variations of the currents with the tides 
and seasons. Ordinarily therefore the current arrows 
shown on charts indicate only the average direction 
and velocity, or possibly only the conditions existing 
at the season when the survey was made. Oceanic 
and coast currents are probably much less uniform 
than might be inferred from the current streams 
drawn on maps and charts. A more systematic 

122 Reading Charts 

investigation of ocean currents is required to fulfill 
the needs of navigation. 

The tidal currents seldom turn with the tides, and 
there may be an interval of as much as three hours 
between the time of high tide or low tide and slack 
water. This leads to the apparent anomaly that in 
cases the current may be running with its greatest 
velocity at the time of high or low water, and may be 
running into a channel for several hours after the tide 
commences to fall. It is therefore, evidently, not safe 
to draw inferences as to currents solely from the tidal 

There are passages where the tidal currents become of 
the greatest importance to navigation, as, for instance, 
in Seymour Narrows on the inside route to Alaska, 
where the current velocity reaches 12 knots and the 
interval of apparent slack water lasts but a few 

Elevations. The unit used for elevations is also 
stated on the face of the chart, as also the plane to 
which elevations are referred. On the United States 
charts this is generally mean high water and on British 
charts the high water of ordinary spring tides. Rocks 
and islets usually have figures shown beside them, 
either in brackets or underscored, which indicate the 
height above high water. Rocks which are bare at 
low water sometimes have a note "dries" or "bares" 
so many feet, indicating their height above low tide, 
although they are covered at high tide. The British 
charts in some regions where there is a large range of 
tide have underlined figures in the area between high 
water and low water indicating the heights above low 

Topography 123 

water, or the depths of water over the bank at high 
water, as explained in each case. 

Topography. The land area on most charts is 
distinguished from the water area by a stipple or tint; 
on some charts the topographic features have, however, 
been depended upon to bring out the land from the 
water. The solid shore line is the high-water line, 
and should be clear on the chart; the area between 
high and low water is sanded or otherwise shaded on 
all charts. The relief of the land is represented by 
hill shading or by contour lines which are the succes- 
sive curves of elevation on the land. Topographic 
symbols are used for some of the more important 
features, such as cliffs, rocky ledges, buildings, bridges, 
trees, roads, etc. It is important for the navigator 
to understand the significance of the hill representation 
and the symbols, as they will aid him in recognizing a 
coast or island, and in identifying landmarks. 

Date of survey and publication. There is usually an 
authority note on each chart showing the source of 
information or date of survey; if on a coast subject to 
change, the latter is important. On the United States 
Coast Survey charts the date of publication of the 
edition is given, and on British and other charts the 
date of both large and small corrections. The chart 
catalogues give the dates of the last editions, or the 
dates of extensive corrections, and this affords a means 
of seeing whether the copy of the chart in use is the 
latest edition available. 


Chart working. In crossing the open and deep por- 
tions of the ocean, where the only data given may be 
the projection lines and soundings far deeper than can 
be reached with navigational sounding machines, the 
chart is used to lay out in advance the general course 
to be followed and to plot the positions of the vessel at 
intervals either as determined by observations or, lack- 
ing these, by dead reckoning. When necessary the 
courses of the vessel are modified as the plotted positions 
are found to fall one side or the other of the proposed 
general track. 

The principal operations on a chart are plotting or 
taking off positions by latitude and longitude, laying 
down or taking off bearings, directions, and courses, 
plotting or measuring distances, and laying down or 
taking off angles. 

To plot a position by its latitude and longitude on 
a mercator chart, set a parallel ruler on the adjacent 
parallel and then move it to the required latitude as 
shown by the border scale at either side; then with a 
pair of dividers at the upper or lower longitude border 
scale take the distance from the nearest meridian and 
lay this distance off along the edge of the parallel ruler. 
The latitude and longitude of a point are taken from the 
chart by reversing this process, or with the dividers 
only. A direction is laid down on the chart or read 
from the chart preferably by using some form of pro- 


Chart Working 125 

tractor and measuring the angle from the projection 
lines. In this country it is more commonly done by 
carrying the direction with a parallel ruler either from 
or to a compass rose printed on the chart. Distances 
are measured or laid down on a mercator chart by using 
the latitude border scale for the middle latitude. On 
polyconic and other larger scale charts distances are 
measured from the scales printed on the chart. It 
should be remarked that in general where special 
accuracy is required distances should be computed and 
not scaled from any chart, because of the error due to 
the distortion of paper in printing. 

The use of protractors on charts in plotting by 
angles in the three-point problem will be referred to 

The course to be steered to allow for a set due to 
current or wind may be obtained by a graphical solution 
on the chart, though it will be preferable to do this on 
other paper, using a larger scale. (Fig. 38.) The direction 
and velocity of the set and the course and speed of the 
ship may be considered as two sides of a parallelogram of 
forces, of which the diagonal is the distance and course 
made good. To obtain the course to steer to reach a 
given point with a given current and speed of vessel, 
lay down the direction of the destination; from the 
starting point lay off the direction of set and the amount 
in one hour; from the extremity of this describe an arc 
with radius equal to the speed of the vessel in one hour. 
A line drawn from the extremity of the direction of 
set to the point of intersection of the arc and the course 
to be made good will give the direction of the course to 
be steered, and the point of intersection will also be the 

126 Use of Charts in Navigation 

estimated position of the vessel at the end of the hour's 

Methods of locating a vessel. The principal methods 
used for locating the position of a vessel are by astro- 
nomical observations, by dead reckoning, by compass 
bearings, by ranges, by horizontal angles, by soundings, 
by vertical angles, and by sound. The full discussion 
of these methods pertains to navigation and pilotage, 
and they will be only briefly referred to here as to their 
graphical application to charts. 

Astronomical methods. There are a number of 
methods of obtaining the position of a vessel by astro- 
nomical observations. When the position is computed 
the chart enters into these only in the plotting of the 
final result, so that with one exception these methods 
will not be referred to further here. 

The elegant method discovered by an American sea- 
man, Captain Sumner, in 1843, is in part graphical, to 
be worked out upon the chart. This method is based 
on the obvious fact that at any instant there is a point 
on the earth having the sun in its zenith and which is 
the center of circles on the earth's surface along the 
circumference of any one of which the sun's altitude is 
the same at all points. A short portion of such a circle 
may be considered as a straight line and can be deter- 
mined by locating one point and its direction, or two 
points in it. This is known as a Sumner line. (Fig. 39.) 

From an observation of the sun's altitude and azi- 
muth and an assumed latitude a position is computed 
and plotted and a line drawn on the chart through this 
position at right angles to the azimuth of the sun as 
taken from the azimuth tables and laid off from a 


Dead Reckoning 129 

meridian. Another method is to compute positions with 
two assumed latitudes and plot the two resulting posi- 
tions and draw a line through them. The vessel must 
be somewhere on the resulting Sumner line. A good 
determination may be obtained by the intersection of 
two Sumner lines obtained from two observations of 
the sun with sufficient interval so that there will be a 
change of azimuth of as much as 30 degrees to give a fair 
intersection. Allowance must be made for the move- 
ment of the vessel between the two observations by 
drawing a line parallel to the first and at a distance 
equal to the distance made good. An excellent inter- 
section may be obtained by observation of the sun, and 
before or after it of a star in the twilight at a different 

Even a single Sumner line, however, furnishes valu- 
able information, as it may be combined with other 
sources of information to obtain an approximation to 
the position. The vessel must be somewhere on this 
line, and this gives a good check on the position by dead 
reckoning, or an intersection may be obtained with a 
line or bearing of a distant land object, or a line of 
soundings may be compared on the chart with the 
Sumner line. 

If an observation is taken when the observed heavenly 
body is bearing abeam, it is evident that the resulting 
Sumner line will be the direction of the course of the 
vessel, and this fact may be useful in shaping the course 
when nearing the land or a danger. 

Dead reckoning. When impossible to obtain the 
position by any other means, it is computed or plotted 
from the last determined position, using the courses 

130 Use of Charts in Navigation 

and distances run as shown by compass and log and 
allowing for effect of current and wind. Because of 
uncertainties in all these elements, positions so obtained 
may be from five to twenty miles in error in a two- 
hundred-mile run, depending of course to some extent 
on the speed of the vessel. 

Compass bearings. A compass bearing of a single 
object, as a lighthouse or a tangent to a point of land, 
laid down on the chart, shows that the vessel is some- 
where on that line, and when combined with other 
information, as with a Sumner line or the course by dead 
reckoning or the distance by a vertical angle, will give 
a position whose correctness of course depends on the 
accuracy of the data used. Bearings of two objects not 
in the same direction give two lines on the chart whose 
intersection is the position. This will be very weak 
if the angle of intersection is acute, and will become 
stronger as it approaches a right angle. A bearing of 
a third object should be taken when practicable, as it 
affords a valuable check in that the three lines should 
intersect in the same point; if they do not do so when 
plotted the error is either in the observations, or the 
compass, or the plotting, or the chart. (Fig. 40). All 
compass bearings are of course dependent upon the 
accuracy of the compass and the knowledge of its errors 
due to the local magnetic effect of the ship, and also 
upon the correctness with which the magnetic variation 
from true north is known. Bearings of near objects 
should therefore always be preferred, and those of dist- 
ant objects considered as giving only approximate posi- 
tions. An error of one degree in the bearing of an object 
30 miles away will deflect the plotted line about one-half 

Compass Bearings 131 

mile. Because of the facility with which they may be 
taken compass bearings are much used for inshore 
navigation, but in point of reliability they are inferior 
to some of the other methods. 

A single or "danger" bearing of an object is often 
a valuable guide in avoiding a danger. For example, 
a reef may lie to the westward of a line drawn South 
10° East from a lighthouse; in approaching a vessel 
will pass safely to the eastward of the reef if the light- 
house is not allowed to bear any to the northward of 
North 10° West. (Fig. 41.) 

Two successive bearings of a single object, as, for 
instance, a lighthouse, noting the distance run in the 
interval, afford a convenient and much used means 
of locating the position with respect to that object. 
Such bearings are drawn on the chart in reversed 
direction from the object. The distance run between 
the bearings, as read by the log and corrected for 
current if practicable, is scaled off with dividers and 
the course of the vessel is set off with parallel ruler; 
the latter is then moved across the two plotted directions 
until the distance intercepted between them equals that 
scaled with the dividers, and the edge of the ruler then 
represents the track of the vessel. (Fig. 42.) If the angle 
from the bow, or from the course of the vessel, for the 
second bearing is double that for the first bearing, the 
distance from the object at the second bearing is equal 
to that run by the vessel in the interval, and the use of 
this simple relation is designated as "doubling the angle 
on the bow." If the angles between the course and 
the object are respectively 45° and 90° when the two 
bearings are taken on an object on the shore, the dis- 

132 Use of Charts in Navigation 

tance that the ship passes offshore when the object 
is abeam is equal to the distance run between the two 
bearings; this is a much used navigational device, 
known as the " bow and beam bearing " or the " four- 
point bearing." There is an advantage, however, 
in using bearings at two and four points (or 22°. 5 
and 45°), as these give the probable distance that the 
object will be passed before it is abeam. 

Ranges. A valuable line of position is obtained by 
noting when two well-situated objects are in range, 
that is, one back of the other in the line of sight from 
the vessel, as, for instance, a church spire appearing 
behind a lighthouse or a rock in line with a prominent 
point. Such ranges are of course entirely free from 
compass errors, and should be noted whenever there is 
favorable opportunity. The value of the range in plot- 
ting will increase with the distance between the objects, 
and if the two are close in proportion to the distance 
to the vessel the direction will be weak owing to the 
uncertainty in drawing a direction through close points. 
Artificial ranges are often erected as aids to navigation, 
usually to indicate the course to be followed in passing 
through a channel. Ranges afford a valuable guide in 
avoiding dangers, as for example an inspection of the 
chart may show that if a certain lighthouse is kept in line 
with or open from an islet a dangerous shoal will be given 
a good berth; on coasts not well buoyed such danger 
ranges are sometimes marked on the charts. (Fig. 43.) 

Horizontal sextant angles. The location of a posi- 
tion by the three-point problem, using sextant angles, 
is much more exact than by bearings, but is less used 
because not so well known and also because additional 

■TO ^•^«-3S.mo3 s.dtqs 

O H 

Horizontal Sexta?it Angles 135 

instruments are required and the conditions are not 
always favorable. It is so valuable a method, however, 
that it should be used, when necessary, on every well- 
equipped vessel. A single horizontal angle taken 
with a sextant between objects, as two lighthouses, 
defines the position of the vessel as somewhere on the 
circumference of a circle passing through the two 
objects and the vessel. A protractor laid on the 
chart with two of its arms set at the observed angle 
and passing through the two objects, will permit of 
locating two or more points of this circle on the chart. 
This furnishes a line of position which may be com- 
bined with other information to locate the vessel. 
With a compass bearing of one of the objects the 
position may be plotted directly from the single angle. 
Two sextant angles measured at the same instant 
between three objects furnish one of the most accurate 
means of locating the position of a vessel, this being 
the same method that is ordinarily used in hydrographic 
surveying, known as the three-point problem. (Fig. 44.) 
The two angles are conveniently set off on a three-arm 
protractor, which is shifted on the chart until the three 
arms touch the three points, when the position of the 
center is plotted. A third angle to a fourth point 
furnishes a valuable check in case of doubt. Two 
angles may also be taken to four objects without any 
common point, and in this case portions of the two 
circles of position are plotted and their intersection 
will be the ship's position. 

The value of this method depends largely on the 
selection of favorably located objects, and it is quite 
important that the principles of the three-point problem 

136 Use of Charts in Navigation 

be understood. If the ship is on or near the circum- 
ference of a circle which passes through the three 
objects the position will be very weak, and the same 
is true if the distance between any two of the objects 
is small as compared with the distance from them to 
the vessel. A useful general rule is that the position 
will be strong if the middle one of the three objects 
is the nearest to the vessel, provided that no two of 
the objects are close together in comparison with the 
distance to the vessel. 

A single sextant angle furnishes a means of avoiding a 
known danger by using what is known as the horizontal 
" danger angle." (Fig. 45.) Note two well-defined objects 
on the coast either side of the danger to be avoided and 
describe a circle through them and passing sufficiently 
outside of the reef to give it a safe berth. With a pro- 
tractor on the chart note the angle between the objects 
at any point on the outer part of this circle. If in 
passing, the angle at the ship between the two objects 
is not allowed to become greater than this "danger 
angle" the danger will be given a sufficient berth. This 
method as well as any use of sextant angles or bearings 
depends of course on the accuracy of the chart, and 
caution must be used where it is not certain that the 
chart depends upon an accurate survey. 

Soundings. Even if objects cannot be seen, due to 
distance or thick weather, the chart furnishes a valuable 
aid when a vessel has approached within the limits 
where it is practicable to obtain soundings. Modern 
navigational sounding machines permit of obtaining 
soundings to depths of nearly one hundred fathoms 
without stopping the vessel. A rough check is at once 

Vertical Angles 139 

obtained by comparing such soundings with those 
given on the chart for the position carried forward by 
dead reckoning, If a number of soundings are taken 
and plotted on a piece of tracing paper, spaced by the 
log readings to the scale of the chart, and this tracing 
paper is laid over the chart and shifted in the vicinity 
of the probable position until the soundings best agree 
with those on the chart, a valuable verification of posi- 
tion may be obtained. This is particularly the case if 
the area has been well surveyed, and the soundings 
taken on the vessel are accurate, and the configuration 
of the bottom has marked characteristics. For instance, 
in approaching New York the crossing of the 30, 20, and 
10 fathom curves will give a fair warning of the distance 
off the Long Island and New Jersey coasts, and sound- 
ings across such a feature as the submerged Hudson 
gorge extending to the southeastward of Sandy Hook 
will give a valuable indication of position. The taking 
of soundings should be resorted to even in favorable 
conditions, in approaching shoal water, as a check on 
other means of locating the vessel. Many marine 
disasters are attributed to failure to make sufficient use 
of the lead, the simplest of navigational aids. 

Vertical angles. The vertical angle of elevation of an 
object whose height is known will give the distance, and 
combined with a bearing or other information this per- 
mits of locating a vessel where better means cannot be 
used. Distance tables are published for this method. 
(Fig. 46.) The vertical angle is measured with a sextant 
and must be the angle at the ship between the top of the 
object and the sea level vertically beneath it; for a hill 
or mountain, therefore, the eye of the observer should 

140 Use of Charts in Navigatio?i 

be near the water. The object should not be so distant 
that curvature becomes appreciable. The "vertical 
danger angle" is a means of avoiding a known danger, 
on a principle similar to that of the horizontal danger 
angle; that is, the angle of elevation of a known object 
is not permitted to become greater than a fixed amount 
depending on the distance from the object to the danger 
to be avoided. 

Positions by sound. In thick weather sound affords 
a valuable aid to the navigator. In narrow passages 
noting the echo of the whistle from a cliff is a method 
resorted to, as for instance in Puget Sound and along 
the Alaska coast. Fog whistles and bell buoys are 
maintained at many places. Submarine bells have 
recently been introduced at a number of points along 
the Atlantic coast, and vessels may be equipped to receive 
these submarine signals transmitted through the water, 
which indicate also the general direction from which 
the sound comes. 

Need of vigilance. Too great importance cannot be 
attached to frequent verification of positions by the best 
available means, particularly when approaching the 
land. Neglect of this or overconfidence has caused 
many disasters. A notable instance was the loss of one 
of the largest Pacific steamers on the coast of Japan in 
March, 1907. In the afternoon of a clear day this 
vessel ran on to a well-known reef about a mile from a 
lighthouse, resulting in the total loss of vessel and cargo 
valued at three and a half million dollars. The captain 
was so confident of his position and that he was giving 
the reef a sufficient berth that he laid down no bearings 
on the chart and took no soundings. 



Instruments 143 

Instruments. The principal instruments needed for 
use with charts are; dividers for taking off distances and 
latitudes and longitudes, parallel ruler for transferring 
directions to or from a compass rose and for taking off 
or plotting the latitude on a mercator chart, protractor of 
180 degrees for reading the angle with the meridian of any 
direction or for laying off on the chart any given angle with 
the meridian, and three-arm or other full-circle protrac- 
tor for plotting a position by the three-point problem. 

Parallel rulers on the principle of Field's are strongly 
recommended for chart work, as they combine in a 
single instrument the advantages of a parallel ruler 
and a 180-degree protractor. Any direction can be 
read or laid off by simply moving the parallel ruler 
to the nearest projection line, which is a process not 
only more convenient than referring to the compass 
rose printed on the chart but also more accurate 
because of the longer radius. These instruments 
can also be used the same as a plain parallel ruler. 
Field's parallel rulers are made in two forms, one rolling 
and the other sliding. The former is a single ruler 
with edge graduated 90 degrees either way, and 
mounted on rollers; it is the most rapid instrument 
for reading or laying off a direction, but it requires 
a smooth surface. The latter is an ordinary two- 
bar parallel ruler with edge when closed graduated 
90 degrees either way; it is a very serviceable instrument 
and probably more to be depended upon for ordinary 
use than the rolling form. Some form of combined 
protractor and parallel ruler should be in every navi- 
gational equipment, and it is unfortunate that these 
instruments are not better known in this country. 

144 Use of Charts in Navigation 

There are other forms of half-circle protractors which 
are used on the same principle, that is, of bringing 
the center on to a projection line and reading where 
the line cuts the border graduation of the protractor. 
Thus a semicircular protractor is used with a separate 
straight edge, along which it is slid to the nearest 
meridian; another form is the simple circular pro- 
tractor with a thread fastened at the center. All these 
forms of protractors, it will be noted, are intended to 
work from the true meridian, and they are usually 
graduated in degrees only; the use of degrees instead 
of points is becoming much more general in navigational 
work, and reference to the true meridian is also more 
common than formerly. 

The standard three-arm protractor, or station 
pointer, as it is known to the English, should be a part 
of every navigational outfit because of its value in 
locating a position by the three-point problem. A 
recent American invention, Court's three-arm pro- 
tractor, is an instrument made of celluloid for the 
same purpose. It should not be considered as a 
substitute for the standard metal instrument, but it 
is a simple, cheap, and handy supplement to it, as it 
may be readily used for small angles and short dis- 
tances where there are mechanical difficulties in work- 
ing with the metal three-arm protractor. Other pro- 
tractors can be used for the three-point problem, as, for 
instance, Cust's protractor on celluloid, on which the 
angles are drawn in pencil and erased, and the tracing- 
paper protractor. 

Degree of reliance on charts. The value of a chart 
must not be judged alone from its general appearance, 

■ -*«». a*-- 

■'m~--..r- '*&*.■" 




Degree of Reliance 147 

as skill in preparation and publication may give a 
handsome appearance to an incomplete survey. On 
the other hand a thorough survey might through poor 
preparation result in a chart defective either in infor- 
mation or in utility. 

The degree of completeness of the soundings, the 
character of the region, and the date of the survey 
should be taken into account in deciding as to the 
amount of reliance to be placed on the chart. Areas 
where the soundings are not distributed with fair 
uniformity may be assumed not to have been completely 
surveyed. Caution should be used in navigating on 
charts where the survey is not complete, and even where 
careful surveys exist care must be taken if the bottom 
is of very irregular nature with lumps near the navi- 
gable depth, as for instance on some of the coral 
reef coasts. Isolated soundings shoaler than the sur- 
rounding depths should be avoided, as there may be 
less water than shown. In such a region, unless the 
whole area is dragged, it is impossible to make it 
entirely certain that all obstructions are charted. 

While an immense amount of faithful work has 
been put into the preparation of many charts, the 
user must constantly exercise his own judgment as to 
the reliance to be placed on them. A coast is not 
to be considered as clear unless it is shown to be; buoys 
may get adrift and be in a different position or be 
gone altogether; fog signals vary in distinctness owing 
to atmospheric conditions; extreme or unusual tides 
may fall below the plane of reference; owing to strong 
winds the actual tide may differ from the predicted 
tide. Errors sometimes creep in from various sources, 

148 Use of Charts in Navigation 

such as those due to different reference longitudes 
or the use of a corrected longitude for a portion of the 
chart without changing other positions to which the 
same correction is applicable; clerical and printing 
errors may occur: there are sometimes omissions in 
surveys; a feature may get plotted in two different 
positions; tide rips are reported as breakers and 
floating objects as rocks or islands, and thus many 
dangers have gotten on the charts which cannot be 
found again, and false reports are sometimes made to 
shield some one from blame. Most of these classes 
of errors and uncertainties, however, disappear in the 
use of charts of a thoroughly surveyed coast. 

Use the latest editions of charts. The latest edition 
of a chart should always be used and should be corrected 
for all notices since its issue. Carelessness or false 
economy in not providing the largest scale or the latest 
chart has been the cause of more than one marine 

The British Board of Trade issue the following 
official notice to shipowners and agents: "The attention 
of the Board of Trade has frequently been called to 
cases in which British vessels have been endangered or 
wrecked through the masters' attempting to navigate 
them by means of antiquated or otherwise defective 
charts. The Board of Trade desires, therefore, to 
direct the especial attention of shipowners and their 
agents to the necessity of seeing that the charts taken or 
sent on board their ships are corrected to the time of 
sailing. Neglect to supply a ship with proper charts 
will be brought prominently before the Court of Inquiry 
in the event of a wreck occurring from that cause." 

Use Latest Editions 149 

The following is a translation of a notice in the 
preface to the catalogue of charts published by the 
German government: "Owners and masters of vessels 
are apprised that cases of marine accidents in which the 
casualty was due to antiquated or erroneous charts, 
have frequently been before the admiralty courts. In 
consequence of this, the ' Instructions for the prevention 
of accidents to steamers and sailing vessels,' issued by 
the Seeberufsgenossenschaft have been amended by the 
following additional paragraph: 'It is obligatory upon 
every master, except when engaged in local coastwise 
navigation, to keep the Notices to Mariners regularly, 
and with the aid of them to carefully keep his charts 
up to date.'" 

The British shipping laws provide that a ship may 
not be sent to sea in such an unseaworthy state that the 
life of any person is thereby endangered, and the House 
of Lords has defined the term "seaworthy" to mean "in 
a fit state as to repairs, equipment, and crew, and in all 
other respects, to encounter the ordinary perils of the 
voyage." Proper charts and sailing directions are a 
necessary part of the equipment of a vessel, and the 
courts have frequently inquired into this. 

The records of the British courts, however, show that 
even in recent years many ships have been damaged 
or lost owing directly or indirectly to failure to have 
the latest information on board. The following are 
instances from these records. 

In 1890 the steamer Dunluce was lost owing to the 
use of an old edition of the Admiralty chart which 
showed a depth of \\ fathoms on the Wikesgrund, 
whereas the later chart showed much less water. In 

150 Use of Charts in Navigation 

this case the master had requested his ship chandler to 
send him the latest chart. 

In 1891 the steamer St. Donats got ashore on a 
patch which was not shown on the chart in use, which 
was privately published in 1881; the danger was, how- 
ever, shown on the Admiralty chart corrected to 1889. 

Also in 1891 the steamer Trent was lost on the 
Missipezza Rock in the Adriatic. The ship was navi- 
gated by a private chart published in 1890 which did 
not show this rock, and by sailing directions published 
in 1866. 

The steamer Aboraca, stranded in the Gulf of 
Bothnia in 1894, was being navigated by a chart cor- 
rected to 1881 which did not show that the Storkalla- 
grund light-vessel had been moved eight miles. 

The steamer Ravenspur was lost on Bilbao Break- 
water owing to the use of a chart not up to date which 
did not show the breakwater. In 1898 the steamer 
Cromarty was lost in attempting to enter Ponta 
Delgada harbor, and in 1901 the steamer "Dinning- 
ton" was lost by steaming on to the new breakwater in 
Portland harbor; both of these disasters were likewise 
due to the use of old charts which did not show the 
breakwaters. In these three cases the masters of the 
vessels had authority to obtain the necessary charts at 
the owners' expense. 

Not so, however, in the following case from the 
finding of a British marine court in 1877: "The primary 
cause of the ship's getting on shore was due to the 
master's being guided in his navigation by an obsolete 
Admiralty chart dated September 1, 1852, and cor- 
rected to April, 1862, and on which no lights are shown 

Use Largest Scale Charts 151 

to exist either in . . . or . . . and to his not being- 
supplied with the latest sailing directions. The Court, 
considering that the master was obliged to furnish 
himself with chronometer, barometer, sextant, charts, 
sailing directions, and everything necessary for the 
navigation of his vessel out of his private resources, 
which, under very favorable circumstances, might per- 
haps reach £150 a year, find themselves unable in this 
instance to pass a heavier censure upon him than that 
he be severely reprimanded." 

The loss of the German steamer Baker on the coast 
of Cuba on January 31, 1908, was declared by the 
marine court at Hamburg to be due in part to the use 
of an unofficial chart which did not show the latest 
surveys on that coast. 

Use the largest scale charts. The largest scale chart 
available should be employed when entering channels, 
bays, or harbors, as it gives information with more 
clearness and detail, positions may be more accurately 
plotted, and sometimes it is the first corrected for new 

The records of the courts of inquiry also show 
cases where vessels have been wrecked owing to the use 
of charts of too small scale. 

In 1890 the steamer Lady Ailsa was lost on the 
Plateau du Four. The only chart on board for this 
locality was a general chart of the Bay of Biscay, 
and the stranding was due to the master's mistaking 
one buoy for another. The court found that the 
chart, although a proper one for general use, was not 
sufficient for the navigation of a vessel in such narrow 
waters and on such a dangerous coast. 

152 Use of Charts in N avigation 

The Zenobia was stranded on the San Thome 
Bank in 1891. On this vessel the owners were to 
furnish the chronometers and the master the charts 
and sailing directions. The master was, however, 
apparently satisfied with only a general chart of the 
South Atlantic for navigation on the coast of Brazil, 
and had no sailing directions at all. 

The depth curves on charts furnish a valuable guide, 
and if the curves are lacking or broken in some parts 
it is usually a sign that the information is incomplete. 
The 100-fathom curve is a general warning of approach 
to the coast. The 10-fathom curve on rocky coasts 
should be considered as a danger curve, and caution 
used after crossing it. The 5-fathom curve is the 
most important for modern vessels of medium draft, 
as it indicates for them the practical limit of naviga- 
tion. The 3, 2, and 1-fathom curves are a guide to 
smaller vessels, but have less significance than formerly 
because of the increase of draft of vessels. 

The shrinkage of paper, especially in plate printing, 
has been referred to. This introduces two possible 
sources of error: first, the shrinkage being different 
in the two directions, any scale printed on the chart 
will be accurate only when used in a direction parallel 
to itself; second, for the same reason, angles and 
directions will be somewhat distorted. Fortunately 
these errors are not serious in the ordinary navigational 
use of a chart, but they should not be overlooked when 
accurate plotting or measuring of distances is attempted 
on a plate-printed chart. 

The actual shrinkage measured on charts printed 
from plates varies from -J- inch to 1 inch in a length 

Care of Charts 153 

of chart of 36 inches. On British and American plate 
printed charts the shrinkage is usually from two to 
nearly three times as much in one direction as it is in 
the other. 

Care of charts. In order that they may be properly 
used charts should be filed flat and not rolled. They 
should be systematically arranged so that the desired 
chart can be instantly found. They should be cared 
for and when in bad condition replaced by new copies. 
They can be most conveniently filed in shallow drawers, 
thus avoiding the placing of many charts in a single 
drawer. The latter is a common fault; it not only 
increases the labor of handling the charts but adds 
to the liability of their injury. 


There are several publications in book and in chart 
form which are either necessary or convenient for use 
in connection with nautical charts. These comprise 
the coast pilots, notices to mariners, tide tables, light 
and buoy lists, and various special charts. 

Coast pilots, or sailing directions, are books giving 
descriptions of the main features, as far as of interest 
to seamen, of the coast and adjacent waters, with 
directions for navigation. They contain much miscel- 
laneous information of value to the mariner, especially 
the stranger. Although they contain additional facts 
which cannot be shown on the charts, they are not at 
all intended to supersede the latter; the mariner should 
in general rely on the charts. The sailing directions 
can be less readily corrected than the charts, and in all 
cases where they differ the charts are to be taken as the 

The most extensive series of sailing directions is 
that published by the British Admiralty, comprising 
fifty-six volumes and including all the navigable regions 
of the world. In the United States the Coast and 
Geodetic Survey publishes ten volumes of coast pilots 
for the Atlantic, Gulf, and Pacific coasts, Porto Rico, 
and southeastern Alaska, and eight volumes of sailing 
directions for Alaska and the Philippine Islands. 
The United States Hydrographic Office publishes six- 


Notices to Mariners 155 

teen volumes of sailing directions for various parts of 
the world. 

Notices to Mariners are published at frequent inter- 
vals, giving all important corrections, which should be 
at once applied by hand to the charts, such as rocks 
or shoals discovered and lights and buoys established 
or moved. New charts, new editions, and canceled 
charts are also announced. 

These notices should be carefully examined and the 
necessary corrections made on all charts of the sets in 
use on the vessel. A chart should be considered as a 
growing rather than a finished instrument, and constant 
watchfulness is required to see that it is kept up to 
date. Neglect of this may cause shipwreck, as the fol- 
lowing instance shows. Report came to Manila in 
1904 that there was a low sand islet lying off the very 
poorly charted northeast coast of Samar; this infor- 
mation was promptly published in the local Notice to 
Mariners. About a month later a small steamer was 
sent to land some native constabulary on that coast. 
The captain failed to obtain or observe this notice, 
and approached the coast before daylight on a course 
which led directly across the sand islet. The vessel 
was driven far up on the sand, where it still lies. 

In the United States, weekly Notices to Mariners 
are published by the Department of Commerce and 
Labor for the coasts under the jurisdiction of the 
United States, and by the Navy Department for all 
regions. These notices are distributed free and can 
be obtained from chart agents and consular officers. 
In Great Britain the notices are published at frequent 
intervals by the Hydrographic Office, and practically 

156 Supplementary Publications 

all countries issuing charts also issue such notices. 
Information as to important changes in lights and 
other announcements of navigational interest are also 
sometimes printed in the marine columns of news- 
papers and in nautical periodicals. 

Tide Tables. Brief information as to the time and 
height of the tide is usually for convenience given on 
the face of the chart. More complete information is 
published in the Tide Tables, with which every navi- 
gator should be provided. "The Tide Tables for 
United States and foreign ports," published annually 
in advance by the United States Coast and Geodetic 
Survey, give complete predictions of the time and 
height of high and low water for each day of the year 
for 70 of the principal ports of the world, and the tidal 
differences from some principal port for 3000 subordi- 
nate ports. The other leading nations also publish 
annual tide tables; those of the British government 
are entitled " Tide Tables for British and Irish ports, 
and also the times of high water for the principal 
places on the globe." 

Light and buoy lists. Brief information as to all 
artificial aids to navigation is shown on the charts. 
Every vessel should also have on board the latest 
official light and buoy lists, which give a more detailed 
description than can be placed on the charts. 

Light and buoy lists for the coasts of the United States 
are published annually by the Light-House Board. 
The United States Hydrographic Office publishes a 
"List of Lights of the World" (excepting the United 
States) , in three volumes. 

The British Hydrographic Office publishes eight 

Chart Catalogues 157 

volumes of Lists of Lights, and these are corrected 

Chart catalogues are published in connection with 
all series of charts. They give the particulars and 
price of each chart published, and are usually arranged 
in geographical order, with both alphabetical and 
numerical indexes, for convenience in finding charts 
either by position, name, or number. 

Charts for special purposes. There are various 
special charts published for the benefit of mariners, 
although not intended for direct use in plotting the 
course of a vessel or in locating its position. Some 
of the more important of these are mentioned below. 

Gnomonic charts are intended solely for laying down 
the great circle or shortest practicable courses between 
points, for which purpose they are very convenient. 
Their use has already been described. The United 
States Hydrographic Office publishes six such charts, 
for the North Atlantic, South Atlantic, Pacific, North 
Pacific, South Pacific, and Indian Oceans. 

Current charts are published by the British Hydro- 
graphic Office for the various oceans; these usually 
show the average ocean currents, but for the Atlantic 
there are monthly and for the Pacific quarterly current 

Magnetic variation charts are published by both the 
United States and British governments. They show 
on a mercator chart of the world the isogonic lines, 
or lines along which the variation of the needle from 
true north is the same. The lines are drawn for each 
degree of variation. The annual change in the varia- 
tion is also indicated. 

158 Supplementary Publications 

Other magnetic charts are published showing the 
lines of equal magnetic dip, horizontal magnetic force, 
and vertical magnetic force. 

Meteorological ocean charts are published by sev- 
eral governments, including the United States, Great 
Britain, and Germany, and give the average weather 
conditions, winds, fogs, currents, ice, tracks of storms, 
and other information. "Pilot charts " of the North 
Atlantic and North Pacific Oceans are issued by the 
United States Hydrographic Office about the first of 
each month, and give "a forecast of the weather for the 
ensuing and a review of that for the preceding month, 
together with all obtainable information as to the most 
available sailing and steam routes, dangers to navigation, 
ice, fog, derelicts, etc., and any additional information 
that may be received of value to navigation." Mariners 
in all parts of the world have joined in contributing 
the information which has been used in compiling 
these pilot charts. 

Track charts are published by the British and 
United States governments. That of the latter is 
entitled " Track and distance chart of the world, show- 
ing the routes traversed by full-powered steamers 
between the principal ports of the world, and the 
corresponding distances." 

Telegraph charts are published showing the " tele- 
graphic connections afforded by the submarine cables 
and the principal overland telegraph lines." 

Index charts are outline plans showing the area 
covered by each chart of a series, and furnish a con- 
venient means of finding a chart of any desired region 
or of selecting the most suitable chart for any purpose. 

Star Charts 159 

These index charts are published either in sets, showing 
all the charts of a series, or are bound into the chart 

Star charts are included in navigational series, 
and are conveniently arranged for use on shipboard 
in identifying the brighter stars. The United States 
Hydrographic Office publishes two, constellations of 
the northern and of the southern hemispheres. 

Explanatory sheets are published in connection 
with various series of charts, giving explanations of 
the symbols and abbreviations used and of other 
important features. In the United States the Coast 
and Geodetic Survey has issued a small pamphlet, 
"Notes on the use of charts," which contains explana- 
tions of its chart symbols, and the Hydrographic Office 
has published " A manual of conventional symbols and 
abbreviations in use on the official charts of the principal 
maritime nations." 



Aids to navigation 118 

Arbitrary projection 79 

Astronomical observations 32 

Astronomical positions 126 

Bearings, position by 130 

Board of Trade notice 148 

Care of charts 153 

Catalogues of charts 157 

Changes in the coast 98 

Chart making, development of . . . . 6 
Chart publications of various 

nations 18 

Charts, earliest nautical 6 

Charts, loxodromic 7 

Charts, plain 8 

Chart schemes 67 

Chart working 124 

Coast and Geodetic Survey, United 

States 13 

Coast pilots 154 

Compass bearings 130 

Compass, nautical use of 6 

Compass, variation of 7 

Compilation of information 67 

Correction of charts, method of . . . . 110 

Cosa, Juan de la 8 

Current charts 157 

Currents . 50, 121 

Danger angle, horizontal 136 

Danger bearing 131 

Danger range 132 

Dangers, reports of 56 

Dates on charts 123 

Dead reckoning 129 



Depth curves 116, 152 

Depths, unit for 19, 116 

Depth units, relation of 118 

Directions on charts 115 

Distances, measured on chart 125 

Distribution of charts 96 

Doubling angle on bow 131 

Draft of vessels 97 

Dragging for dangers 55 

Earthquakes 109 

Electrotyping plates 89 

Elevations 122 

Engraving machines 89 

Engraving on copper 84 

Engraving on stone 93 

Eskimo map 1 

Etching on copper 95 

Explanatory sheets 159 

Flattening of the earth 3 

France, establishment of chart office 10 

Geographic position on charts 115 

Geography, early 2 

Germany, contributions to hydrog- 
raphy 14 

Gnomonic charts . 79, 157 

Gnomonic projection 74 

Great Britain, contributions to 

geography „ 14 

Holland, development of chart 

making 10 

Hydrographic Office, British 13 

Hydrographic Office, United States 13 

Hydrography 40 




Index charts 158 

Information on charts 23 

Instruments used on charts 141 

Lake Survey, United States 13 

Largest scale chart 151 

Latest editions of charts 148 

Light and buoy lists 156 

Lithographic printing 94 

Locating a vessel 126 

Longitude, initial 19 

Longitude, uncertainties in 10 

Magnetic charts 157 

Magnetic variation 56 

Map, earliest 2 

Map making, development of 2 

Maps, need of 1 

Maritime surveys, extension of 17 

Mercator chart, history 8 

Mercator projection . 68 

Meteorological charts (pilot charts) 158 

Navigation, use of charts in 124 

Notices to mariners Ill, 155 

Paper, shrinkage of 152 

Parallel rulers, Field's 141 

Photolithography 93 

Plane of reference 20, 1 19 

Plotting positions 124 

Polyconic projection 73 

Printing, plate 84, 90 

Privately published charts 21 

Progress of hydrographic surveys. . 17 

Projection, explanation of 114 

Projections 68, 114 

Protractor, three-arm 144 

Ptolemy 3 

Publication of charts, methods 84 

Purpose of charts 22 

Ranges 132 

Reading charts 112 


Reliance on charts 144 

Reports of dangers, erroneous 57 

Requirements for charts 23 

Revision of charts, need of 97 

Rock, Brooklyn 50 

Sailing directions, early 4 

Sailing directions 154 

Scale equivalents 113 

Scales of charts 79, 112 

Set, graphical allowance for 125 

Sextant angles 132 

Sheets for surveys 39 

Shrinkage of paper 152 

Sound, position by 140 

Sounding machines 49 

Soundings, position by 136 

Star charts 159 

Station pointer 144 

Steamer for surveying 49 

Sumner's method 126 

Supplementary publications 154 

Surveys on foreign coasts 14 

Surveys, need of thorough 31 

Symbols on charts 20 

Telegraph charts 158 

Three-point problem 132, 135 

Tides 50, 120 

Tide tables 156 

Topography 39 

Topography on charts 123 

Track charts 158 

Triangidation 32 

Uniformity in charts 21 

Use of charts in navigation 124 

Vertical angles 139 

Vigias, removal of 62 

Vigilance, need of 140 

Volcanic action 109 

Wrecks due to deficient charts 149 






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Armsby's Manual of Cattle-feeding i2mo, Si 75 

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Part II. Systematic Pomology i2mo, 1 50 

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Grotenfelt's Principles of Modern Dairy Practice. (Woll.) i2mo, 2 00 

Hanausek's Microscopy of Technical Products. (Winton.) .8vo, 5 oo> 

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Maynard's Landscape Gardening as Applied to Home Decoration i2mo, 1 50 

* McKay and Larsen's Principles and Practice of Butter-making 8vo, 1 50 

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Stockbridge's Rocks and Soils 8vo, 2 50 

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French and Ives's Stereotomy 8vo, 2 50 

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Sanitation of Public Buildings . i2mo, 1 50 

Theatre Fires and Panics i2mo, 1 50 

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Johnson's Statics by Algebraic and Graphic Methods 8vo, 2 00 

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Merrill's Stones for Building and Decoration . .8vo, 5 00 

Non-metallic Minerals : Their Occurrence and Uses 8vo, 4 00 

Monckton's Stair-building 4to, 4 00 

Patton's Practical Treatise on Foundations 8vo, 5 00 

Peabody's Naval Architecture 8vo, 7 50 

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Snow's Principal Species of Wood 8vo, 3 50 

Sondericker's Graphic Statics with Applications to Trusses, Beams, and Arches. 

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Towne's Locks and Builders' Hardware i8mo, morocco, 3 00 

Turneaure and Maurer's Principles of Reinforced Concrete Construc- 
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Wait's Engineering and Architectural Jurisprudence 8vo, 6 00 

Sheep, 6 so 
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Law of Contracts 8vo, 3 00 

Wilson's Air Conditioning, iln Press.) 

Wood's Rustless Coatings: Corrosion and Electrolysis of Iron and Steel. .8vo, 4 00 
Worcester and Atkinson's Small Hospitals, Establishment and Maintenance, 
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The World's Columbian Exposition of 1893 Large 4to, 1 00 


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Hamilton's The Gunner's Catechism i8mo, 

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Nixon's Adjutants' Manual 24010, 

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Powell's Army Officer's Examiner i2mo, 

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Wheeler's Siege Operations and Military Mining 8vo, 

Winthrop's Abridgment of Military Law i2mo, 

Woodhull's Notes on Military Hygiene i6mo, 

Young's Simple Elements of Navigation i6mo, morocco, 


Fletcher's Practical Instructions in Quantitative Assaying with the Blowpipe. 

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Furman's Manual of Practical Assaying 8vo, 

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Low's Technical Methods of Ore Analysis 8vo, 

Miller's Manual of Assaying. .'. i2mo, 

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O'Driscoli's Notes on the Treatment of Gold Ores 8vo, 

Ricketts and Miller's Notes on Assaying 8vo, 

Robine and Lenglen's Cyanide Industry. (Le Clerc.) 8vo, 

TJlke's Modern Electrolytic Copper Refining 8vo, 

Wilson's Cyanide Processes i2mo, 

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Comstock's Field Astronomy for Engineers 8vo, 2 50 

Craig's Azimuth 4 to, 3 50. 

Crandall's Text-book on Geodesy and Least Squares 8vo, 3 00 

Doolittle's Treatise on Practical Astronomy 8vo, 4 oo> 

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Hayford's Text-book of Geodetic Astronomy 8vo, 3 00 

Merrirran's Elements of Precise Surveying and Geodesy 8vo, 2 50 

* Michie and Harlow's Practical Astronomy 8vo, 3 00 

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Davenport's Statistical Methods, with Special Reference to Biological Variation. 

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Thome and Bennett's Structural and Physiological Botany i6mo, 2 25 

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Austen's Notes for Chemical Students nmo, 1 50 

Beard's Mine Gases and Explosions. (In Press.) 

Bernadou's Smokeless Powder. — Nitro-cellulose, and Theory of the Cellulose 

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Bolduan's Immune Sera 12mo, ] 50 

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Brush and Penfield's Manual of Determinative Mineralogy 8vo, 4 00 

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Classen's Quantitative Chemical Analysis by Electrolysis. (Boltwood.) . .8vo, 3 00 

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Furman's Manual of Practical Assaying 8vo, 3 00 

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Hopkins's Oil-chemists' Handbook 8vo, 3 00 

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Jackson's Directions for Laboratory Work in Physiological Chemistry. .8vo, 1 25 
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Keep's Cast Iran 8vo, 2 50 

Xadd's Manual of Quantitative Chemical Analysis i2mo, 1 00 

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Leach's The Inspection and Analysis of Food with Special Reference to State 

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Mandel's Handbook for Bio-chemical Laboratory i2mo, 1 50 

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Elements of Physical Chemistry nmo, 3 00 

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Riggs's Elementary Manual for the Chemical Laboratory 8vo, 1 25 

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Ruddiman's Incompatibilities in Prescriptions 8vo, 

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Schimpf's Text-book of Volumetric Analysis , i2mo. 

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Smith's Lecture Notes on Chemistry for Dental Students 8vo, 

Spencer's Handbook for Chemists of Beet-sugar Houses i6mo, morocco 

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Stockbridge's Rocks and Soils 8vo, 

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Short Course in Inorganic Qualitative Chemical Analysis for Engineering 

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Whipple's Microscopy of Drinking-water 8vo, 

Wilson's Cyanide Processes nmo, 

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Wulling's Elementary Course in Inorganic, Pharmaceutical, and Medical 
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Hayford's Text-book of Geodetic Astronomy 8vo, 3 00 





























































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Howe's Retaining Walls for Earth i2mo, 

Boyt and Grover's River Discharge 8vo, 

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Ives and Hilts's Problems in Surveying i6mo, morocco, 

Johnson's (J. B.) Theory and Practice of Surveying Small 8vo, 

Johnson's (L. J.) Statics by Algebraic and Graphic Methods 8vo, 

Laplace's Philosophical Essay on Probabilities. (Truscott and Emory.) . nmo, 
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Ogden's Sewer Design i2mo, 

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Patton's Treatise on Civil Engineering 8vo half leather, 

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Wait's Engineering and Architectural Jurisprudence 8vo, 

Law of Operations Preliminary to Construction in Engineering and Archi- 
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Law of Contracts 8vo, 

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i6mo, morocco, 
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Boiler's Practical Treatise on the Construction of Iron Highway Bridges . .8vo, 2 00 

J3urr and Falk's Influence Lines for Bridge and Roof Computations 8vo, 3 00 

Design and Construction of Metallic Bridges 8vo, 5 00 

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Greene's Roof Trusses 8vo, 1 25 

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Howe's Treatise on Arches. . 8vo, 4 00 

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Johnson, Bryan, and Turneaure's Theory and Practice in the Designing of 

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Merriman and Jacoby's Text-book on Roofs and Bridges : 

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Part II. Graphic Statics :8vo, 2 50 

Part III. Bridge Design 8vo, 2 50 

Part TV. Higher Structures 8vOj 2 50 





































































Morison's Memphis Bridge 4to, 10 oo> 

WaddelFs De Pontibus, a Pocket-book for Bridge Engineers . . i6mo, morocco, 2 00 

* Specifications for Steel Bridges nmo, 5c* 

Wright's Designing of Draw-spans. Two parts in one volume 8vo, 3 50- 


Barnes's Ice Formation 8vo, 3 oo> 

Bazin's Experiments upon the Contraction of the Liquid Vein Issuing from 

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Bovey's Treatise on Hydraulics 8vo, 5 oo- 

Church's Mechanics of Engineering 8vo, 6 oo- 

Diagrams of Mean Velocity of Water in Open Channels paper, 1 so- 
Hydraulic Motors. 8vo, 2 oo- 

Coffin's Graphical Solution of Hydraulic Problems i6mo, morocco, 2 50 

Flather's Dynamometers, and the Measurement of Power nmo, 3 00 

Folwell's Water-supply Engineering 8vo, 4 00 

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Fuertes's Water and Public Health i2mo, 1 50 

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Hazlehurst's Towers and Tanks for Water-works 8vo, 2 50- 

Herschel's 115 Experiments on the Carrying Capacity of Large, Riveted, Metal 

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Merriman's Treatise on Hydraulics 8vo, 5 00 

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Schuyler's Reservoirs for Irrigation, Water-power, and Domestic Water- 
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Turneaure and Russell's Public Water-supplies 8vo, 5 oo- 

Wegmann's Design and Construction of Dams. 5th Edition, enlarged. . .4to, 6 oo- 

Water-supply of the City of New York from 1658 to 1895 410, 10 oo- 

Whipple's Value of Pure Water Large i2mo, 1 00 

Williams and Hazen's Hydraulic Tables 8vo, 1 50- 

Wilson's Irrigation Engineering , Small 8vo, 4 oo» 

Wolff's Windmill as a Prime Mover 8vo, 3 oo- 

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Elements of Analytical Mechanics 8vo, 3 oo- 


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